Biomass Conversion and Biorefinery

, Volume 2, Issue 3, pp 229–244 | Cite as

Cold flow model investigations of the countercurrent flow of a dual circulating fluidized bed gasifier

  • Johannes C. Schmid
  • Tobias Pröll
  • Hannes Kitzler
  • Christoph Pfeifer
  • Hermann Hofbauer
Original Article


A novel fluidized bed gasification concept with enhanced gas–particle interaction combining two circulating fluidized bed reactors is proposed. Cold flow model results show the feasibility of the concept with regard to fluid dynamics. The aim of the design is to generate a nitrogen (N2) free product gas with low tars and fines contents. Therefore, the system is divided into an air/combustion and a fuel/gasification reactor. Two gas streams are obtained separately. The two reactors are interconnected via loop seals to assure the global circulation of bed material and to avoid gas leakages from one reactor to the other. The global circulation rate is driven by the gas velocity in the air/combustion reactor. Furthermore, the fuel/gasification reactor itself is a circulating fluidized bed with the special characteristic of almost countercurrent flow conditions for the gas phase and bed material particles. By simple geometrical modifications, it is possible to achieve well-mixed flow conditions in the fuel/gasification reactor along the full height. The gas velocity and the geometrical properties in the fuel/gasification reactor are chosen in such a way that the entrainment of coarse particles is low at the top. Due to the dispersed downward movement of the bed material particles and the feedstock input at defined locations of the fuel/gasification reactor, no volatiles are produced in the upper regions and the problems of insufficient gas phase conversion and high tar contents are avoided.


Fluidization Circulating fluidized bed Dual fluidized bed Countercurrent gas–particle movement Gasification Sorption enhanced reforming 




Free cross section, m2


Constricted cross section, m2


Aperture ratio, –


Archimedes number, –


Riser free diameter, m


Constricted diameter, m


Dimensionless particle diameter, –


Particles mean diameter, m


Pressure drop, mbar


Void fraction, voidage, –

(1 − ε)

Particle volume fraction, –


Modified Froude number, –


Gravity constant, g = 9.81, m/s2


Particle mass flux, circulation rate, kg/(m2 s)

\( {{\dot{m}}_{\text{p}}} \)

Particle mass flow, kg/h


Reynolds number, –


Superficial gas velocity, m/s


Dimensionless gas velocity, –


Minimum bubbling velocity, m/s


Minimum fluidization velocity, m/s


Terminal velocity, m/s

\( {{\dot{V}}_{\text{g}}} \)

Gas volume flow, m3/h


Kinematic gas viscosity, m2/s


Gas density, kg/m3


Particle density, kg/m3

(ρp − ρg)/ρg

Density ratio, –


Sphericity of particles, –



Absolute pressure fluctuations


Air/combustion reactor


Compressed Air and Gas Institute


Circulating fluidized bed


Cold flow model


Chemical looping combustion


Chemical looping reforming


Dual circulating fluidized bed


Dual fluidized bed


Differential pressure fluctuations


US Environmental Protection Agency


Fuel/gasification reactor


Internal loop seal


Lower loop seal


National Bureau of Standards


National Institute of Standards and Technology


Standard ambient temperature and pressure


Sorption enhanced reforming


Upper loop seal



This work is part of the projects G-volution II and ERBA which are being conducted within the “New Energies 2020” research calls funded by the Austrian Climate and Energy Fund and processed by the Austrian Research Promotion Agency (FFG). The work has been accomplished in cooperation with TECON Engineering GmbH, voestalpine Stahl GmbH, and voestalpine Stahl Donawitz GmbH & Co KG.


  1. 1.
    Wilk V, Kitzler H, Koppatz S, Pfeifer C, Hofbauer H (2011) Gasification of waste wood and bark in a dual fluidized bed steam gasifier. Biomass Convers Biorefinery 1(2):91–97. doi: 10.1007/s13399-011-0009-z CrossRefGoogle Scholar
  2. 2.
    Schmid JC, Wolfesberger U, Koppatz S, Pfeifer C, Hofbauer H (2012) Variation of feedstock in a dual fluidized bed steam gasifier—influence on product gas, tar content and composition. Environ Progr Sustain Energy. doi: 10.1002/ep.11607
  3. 3.
    Brown RC (2011) Thermochemical processing of biomass: conversion into fuels, chemicals and power. Wiley, Chichester. doi: 10.1002/9781119990840. ISBN 9780470721117CrossRefGoogle Scholar
  4. 4.
    Hofbauer H, Stoiber H, Veronik G (1995) Gasification of organic material in a novel fluidization bed system. Proc. 1st SCEJ Symposium on Fluidization, Tokyo, pp 291–299Google Scholar
  5. 5.
    Kirnbauer F, Wilk V, Kitzler H, Kern S, Hofbauer H (2012) The positive effects of bed material coating on tar reduction in a dual fluidized bed gasifier. Fuel 95:553–562. doi: 10.1016/j.fuel.2011.10.066 CrossRefGoogle Scholar
  6. 6.
    Grace JR (1986) Contacting modes and behaviour classification of gas–solid and other two-phase suspensions. Can J Chem Eng 64:353–363. doi: 10.1002/cjce.5450640301 CrossRefGoogle Scholar
  7. 7.
    Lim KS, Zhu JX, Grace JR (1995) Hydrodynamics of gas–solid fluidization. Int J Multiphase Flow 2l:141–193. doi: 10.1016/0301-9322(95)00038-Y CrossRefGoogle Scholar
  8. 8.
    Kunii D, Levenspiel O (1997) Circulating fluidized-bed reactors. Chem Eng Sci 52(15):2471–2482. doi: 10.1016/S0009-2509(97)00066-3 CrossRefGoogle Scholar
  9. 9.
    Lewis WK, Gilliland ER, Bauer WC (1949) Characteristics of fluidized particles. Ind Eng Chem 41(6):1104–1117. doi: 10.1021/ie50474a004 CrossRefGoogle Scholar
  10. 10.
    Grace JR (1990) High-velocity fluidized bed reactors. Chem Eng Sci 45(8):1953–1966. doi: 10.1016/0009-2509(90)80070-U CrossRefGoogle Scholar
  11. 11.
    Schlichthaerle P, Werther J (1999) Axial pressure profiles and solids concentration distributions in the CFB bottom zone. Chem Eng Sci 54(22):5485–5493. doi: 10.1016/S0009-2509(99)00289-4 CrossRefGoogle Scholar
  12. 12.
    Johansson A, Johnsson F, Leckner B (2007) Solids back-mixing in CFB boilers. Chem Eng Sci 62(1/2):561–573. doi: 10.1016/j.ces.2006.09.021 Google Scholar
  13. 13.
    Kolbitsch P, Pröll T, Hofbauer H (2008) Modeling of a 120 kW chemical looping combustion reactor system using a NiO oxygen carrier. Chem Eng Sci 64(1):99–108. doi: 10.1016/j.ces.2008.09.014 Google Scholar
  14. 14.
    Corella J, Aznar MP, Gil J, Caballero MA (1999) Biomass gasification in fluidized bed: where to locate the dolomite to improve gasification. Energy Fuel 13(6). doi: 10.1021/ef990019r
  15. 15.
    Pfeifer C, Koppatz S, Hofbauer H (2011) Catalysts for dual fluidized bed biomass gasification—an experimental study at the pilot plant scale. Biomass Convers Biorefinery 1(2):63–74. doi: 10.1007/s13399-011-0005-3 CrossRefGoogle Scholar
  16. 16.
    Pfeifer C, Schmid JC, Pröll T, Hofbauer H (2011) Next generation biomass gasifier. Proc. 19th European Biomass Conference, Berlin, GermanyGoogle Scholar
  17. 17.
    Lyngfeld A, Thunman H (2005) Construction and 100 h of operational experience of a 10-kW chemical-looping combustor. In: Thomas DC (ed) Carbon dioxide capture for storage in deep geologic formations. Elsevier, Amsterdam, pp 625–645. doi: 10.1016/B978-008044570-0/50122-7, chapter 36Google Scholar
  18. 18.
    Pröll T, Kolbitsch P, Bolhàr-Nordenkampf J, Hofbauer H (2009) A novel dual circulating fluidized bed (DCFB) system for chemical looping processes. AICHE J 55(12):3255–3266. doi: 10.1002/aic.11934 CrossRefGoogle Scholar
  19. 19.
    Reh L (1961) Das Wirbeln von körnigem Gut im schlanken Diffusor als Grenzzustand zwischen Wirbelschicht und pneumatischer Förderung. Dissertation, TH Karlsruhe, GermanyGoogle Scholar
  20. 20.
    Grace JR (1982) Fluidized bed hydrodynamics. In: Hetsroni G (ed) Handbook of multiphase systems, chapter 8.1. Hemisphere, Washington, DCGoogle Scholar
  21. 21.
    Haider A, Levenspiel O (1989) Drag coefficient and terminal velocity of spherical and nonspherical particles. Powder Technol 58(1):63–70. doi: 10.1016/0032-5910(89)80008-7 CrossRefGoogle Scholar
  22. 22.
    Yang WC (2007) Modification and re-interpretation of Geldart’s classification of powders. Powder Technol 171(2):59–74. doi: 10.1016/j.powtec.2006.08.024 CrossRefGoogle Scholar
  23. 23.
    Geldart D (1973) Types of gas fluidization. Powder Technol 7(5):285–292. doi: 10.1016/0032-5910(73)80037-3 CrossRefGoogle Scholar
  24. 24.
    Bi HT, Grace JR (1995) Flow regime diagrams for gas–solid fluidization and upward transport. Int J Multiphase Flow 21(6):1229–1236. doi: 10.1016/0301-9322(95)00037-X zbMATHCrossRefGoogle Scholar
  25. 25.
    Bi HT, Grace JR (1995) Effect of measurement method on the velocities used to demarcate the onset of turbulent fluidization. Chem Eng J 57(3):261–271. doi: 10.1016/0923-0467(94)02875-B Google Scholar
  26. 26.
    Ellis N, Bi HT, Lim CJ, Grace JR (2004) Hydrodynamics of turbulent fluidized beds of different diameters. Powder Technol 141(1/2):124–136. doi: 10.1016/j.powtec.2004.03.001 CrossRefGoogle Scholar
  27. 27.
    Bi HT, Ellis N, Abba IA, Grace JR (2000) A state-of-the-art review of gas–solid turbulent fluidization. Chem Eng Sci 55(21):4789–4825. doi: 10.1016/S0009-2509(00)00107-X CrossRefGoogle Scholar
  28. 28.
    Rabinovich E, Kalman H (2011) Flow regime diagram for vertical pneumatic conveying and fluidized bed systems. Powder Technol 207(1–3):119–133. doi: 10.1016/j.powtec.2010.10.017 CrossRefGoogle Scholar
  29. 29.
    Klinzing GE, Marcus RD, Rizk F, Leung LS (1997) Pneumatic conveying of solids: a theoretical and practical approach, 2nd edn. Chapman & Hall, London. ISBN 0-412-72440-5Google Scholar
  30. 30.
    Rautiainen A, Graeme S, Poikolainen V, Sarkomaa P (1999) An experimental study of vertical pneumatic conveying. Powder Technol 104(2):139–150. doi: 10.1016/S0032-5910(99)00056-X CrossRefGoogle Scholar
  31. 31.
    Abba IA, Grace JR, Bi HT, Thompson ML (2003) Spanning the flow regimes: generic fluidized-bed reactor model. AICHE J 49(7):1838–1848. doi: 10.1002/aic.690490720 CrossRefGoogle Scholar
  32. 32.
    Göransson K, Söderlind U, He J, Zhang W (2010) Review of syngas production via biomass DFBGs. Renew Sust Energ Rev 15(1):482–492. doi: 10.1016/j.rser.2010.09.032 CrossRefGoogle Scholar
  33. 33.
    Schmid JC, Pröll T, Pfeifer C, Hofbauer H (2011) Improvement of gas–solid interaction in dual circulating fluidized bed systems. Proc. 9th European Conference on Industrial Furnaces and Boilers (INFUB), Estoril, PortugalGoogle Scholar
  34. 34.
    Lewis WK, Gilliland ER (1950) Conversion of hydrocarbons with suspended catalyst. US Patent No. 2498088Google Scholar
  35. 35.
    Bu J, Zhu JX (1999) Influence of ring-type internals on axial pressure distribution in circulating fluidized bed. Can J Chem Eng 77(1):26–34. doi: 10.1002/cjce.5450770106 CrossRefGoogle Scholar
  36. 36.
    Pröll T, Schmid JC, Pfeifer C, Hofbauer H (2010) Design considerations for direct solid fuel chemical looping combustion systems. High temperature solid looping cycles network, 2nd network meeting, Alkmaar, NetherlandsGoogle Scholar
  37. 37.
    Pröll T, Rupanovits K, Kolbitsch P, Bolhàr-Nordenkampf J, Hofbauer H (2009) Cold flow model study on a dual circulating fluidized bed system for chemical looping processes. Chem Eng Technol 32(3):418–424. doi: 10.1002/ceat.200800521 CrossRefGoogle Scholar
  38. 38.
    Guìo-Pèrez DC, Marx K, Pröll T, Hofbauer H (2011) Fluid dynamic effects of ring-type internals in a dual circulating fluidized bed system. Proc. 10th International Conference on Circulating Fluidized Beds and Fluidization Technology (CFB-10), Sunriver, Oregon, USAGoogle Scholar
  39. 39.
    Jiang P, Bi HT, Jean RH, Fan LS (1991) Baffle effects on performance of catalytic circulating fluidized bed reactor. AICHE J 37(9):1392–1400. doi: 10.1002/aic.690370911 CrossRefGoogle Scholar
  40. 40.
    Zhu JX, Salah M, Zhou Y (1997) Radial and axial voidage distributions in circulating fluidized bed with ring-type internals. J Chem Eng Jpn 30(5):928–937. doi: 10.1252/jcej.30.928 CrossRefGoogle Scholar
  41. 41.
    Kersten RA, Prins W, van der Drift B, van Swaaij WPM (2003) Principles of a novel multistage circulating fluidized bed reactor for biomass gasification. Chem Eng Sci 58(3–6):725–731. doi: 10.1016/S0009-2509(02)00601-2 Google Scholar
  42. 42.
    Bi H, Cui H, Grace JR, Kern A, Lim CJ, Rusnell D, Song X, McKnight C (2004) Flooding of gas–solids countercurrent flow in fluidized beds. Ind Eng Chem Res 43(18):5611–5619. doi: 10.1021/ie030772e CrossRefGoogle Scholar
  43. 43.
    Bi X (2011) A generalized flow regime diagram for fluid–solid vertical transport. Proc. 10th International Conference on Circulating Fluidized Beds and Fluidization Technology (CFB-10), Sunriver, Oregon, USAGoogle Scholar
  44. 44.
    Glicksman LR (1984) Scaling relationships for fluidized beds. Chem Eng Sci 39(9):1373–1379. doi: 10.1016/0009-2509(84)80070-6 CrossRefGoogle Scholar
  45. 45.
    Glicksman LR, Hyre M, Woloshun K (1993) Simplified scaling relationships for fluidized beds. Powder Technol 77(2):177–199. doi: 10.1016/0032-5910(93)80055-F CrossRefGoogle Scholar
  46. 46.
    Leckner B, Werther J (2000) Scale-up of circulating fluidized bed combustion. Energy Fuel 14(6):1286–1292. doi: 10.1021/ef0001078 CrossRefGoogle Scholar
  47. 47.
    Penthor S, Pröll T, Hofbauer H (2011) Chemical-looping combustion using biomass as fuel. 2nd Oxyfuel Combustion Conference (OCC2), Yeppoon, Queensland, AustraliaGoogle Scholar

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Johannes C. Schmid
    • 1
  • Tobias Pröll
    • 1
  • Hannes Kitzler
    • 1
  • Christoph Pfeifer
    • 1
  • Hermann Hofbauer
    • 1
  1. 1.Institute of Chemical EngineeringVienna University of TechnologyViennaAustria

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