Investigation of bubble diameter and flow regime between water and dilute aqueous ethanol solutions in an airlift reactor

Abstract

In this study, the effect of ethanol addition into pure water and its concentration on bubble diameter, gas hold-up and flow regimes were investigated in an airlift reactor. Air and water with ethanol (concentration ranging from 0%–1%, v/v) were as dispersed and continuous phases, respectively. Superficial gas velocity was considered as an effective parameter. Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas. Alcohol concentration enhancement caused bubble diameter to decrease. Furthermore, the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1% (v/v) and also was 3.4 times higher than that of ethanol with concentration of 0.25% (v/v) at the highest aeration gas velocity inlet. For ethanol solutions in lower superficial gas velocity, a homogenous flow regime was observed. This trend continued to inlet gas velocity of about 0.4 cm/s. The transition flow regime occurred after this datum although in pure water, a homogenous flow regime was observed up to a superficial gas velocity of 0.7 cm/s. The gas hold-up in dilute ethanol solutions were more than (around 2 times) that of pure water and increased with increasing concentration of ethanol in those solutions.

Key words： airlift rector; bubble diameter; gas hold-up; flow regime; ethanol

Acknowledgments

The authors thank the Arak University for facilities preparation and financial support.

References

1 Camarasa E, Carvalho E, Meleiro L A C, Maciel Filho R, Domingues A, Wild G, Poncin S, Midoux N, Bouillard J. Development of a complete model for an air-lift reactor. Chemical Engineering Science, 2001, 56(2): 493-502

2 Loh K H, Liu J. External loop inversed fluidized bed airlift bioreactor (EIFBAB) for treating high strength phenolic waste water. Chemical Engineering Science, 2001, 56(21-22): 6171-6176

3 Zhang Z, Zhou J, Wang J, Guo H, Tong J. Integration of nitrification and denitrifying dephosphatation in air lift loop sequencing batch biofilm reactor. Process Biochemistry (Barking, London, England), 2006, 41(3): 599-608

4 Lo C S, Hwang S J. Degradation of waste gas containing toluene in an airlift bioreactor. Environmental Science & Technology, 2004, 38(7): 2271-2280

PMID

5 Chisti Y, Moo-Young M. Airlift reactors: characteristics, applications, and design considerations. Chemical Engineering Communications, 1987, 60(1): 195-242

6 Jones S T. Gas-liquid mass transfer in an external airlift loop reactor for syngas fermentation. Dissertation for the Doctoral Degree.Iowa: Iowa State University, 2007, 6-24

7 Kluytmans J H J, van Wachem B G M, Kuster B F M, Schouten J C. Design of an industrial size airlift loop redox cycle (ALRC) reactor for catalytic alcohol oxidation and catalyst reactivation. Industrial & Engineering Chemistry Research, 2003, 42(18): 4174-4185

8 Choi K H. Hydrodynamic and mass transfer characteristics of external-loop airlift, reactors without an extension tube above the down-comer. Korean J Chem Eng, 2001, 18(2): 240-246

9 Abashar M E, Narsingh U, Rouillard A E, Judd R. Hydrodynamic flow regimes, gas hold-up, and liquid circulation in airlift reactors. Industrial & Engineering Chemistry Research, 1998, 37(4): 1251-1259

10 Vial C, Poncin S, Wild G, Midoux N. Experimental and theoretical analysis of axial dispersion in the liquid phase in external-loop airlift reactors. Chemical Engineering Science, 2005, 60(22): 5945-5954

11 van Benthum W A J, van der Lans R G J M. van lossdrecht M C M, Heijnen J J. Bubble recirculation regimes in an internal-loop airlift reactor. Chemical Engineering Science, 1999, 54(18): 3995-4006

12 Jin B, Lant P. Flow regime, hydrodynamics, floc size distribution and sludge properties in activated sludge bubble column, air-lift and aerated stirred reactors. Chemical Engineering Science, 2004, 59(12): 2379-2388

13 Sotiriadis A A, Thorpe R B, Smith J M. Bubble size and mass transfer characteristics of sparged down wards two-phase flow. Chemical Engineering Science, 2005, 60(22): 5917-5929

14 Homayouni S S, Mehrnia M R, Mostoufi N, Rajabi M, Yazdani A. Bubble size distribution in oil-based bubble columns. Chemical Engineering & Technology, 2008, 31(11): 1668-1675

15 Ruen-ngam D, Wongsuchoto P, Limpanuphap A, Charinpanitkul T, Pavasant P. Influence of salinity on bubble size distribution and gas–liquid mass transfer in airlift contactors. Chemical Engineering Journal, 2008, 141(1-3): 222-232

16 Farrell A E, Plevin R J, Turner B T, Jones A D, O’Hare M, Kammen D M. Ethanol can contribute to energy and environmental goals. Science, 2006, 311(5760): 506-508

PMID

17 Rao K, Chaudhari V, Varanasi S, Kim D S. Enhanced ethanol fermentation of brewery wastewater using the genetically modified strain E. coli KO11. Applied Microbiology and Biotechnology, 2007, 74(1): 50-60

PMID

18 Lessard R R, Zieminski S A. Bubble coalescence and gas transfer in aqueous electrolyte solutions. Industrial & Engineering Chemistry Fundamentals, 1971, 10(2): 260-269

19 Eren H. Particle concentration characteristics and density measurements of slurries using electromagnetic flowmeters. IEEE Transactions on Instrumentation and Measurement, 1995, 44(3): 783-786

20 Burattini L, Bini S, Burattini R. Correlation method versus enhanced modified moving average method for automatic detection of T-wave alternans. Computer Methods and Programs in Biomedicine, 2010, 98(1): 94-102

PMID

21 Winters P R. Forecasting sales by exponentially weighted moving averages. Management Science, 1960, 6(3): 324-342

22 Zuber N, Findlay J. Average volumetric concentration in two-phase flow systems. ASME J Heat Trans, 1965, 87: 453-468

23 Biswas A B, Das S K. Hold up characteristics of gas non-Newtonian liquid flow through helical coils in vertical orientation. Industrial & Engineering Chemistry Research, 2006, 45(21): 7287-7292

24 Atenas M, Clark M, Lazarova V. Hold-up and liquid circulation velocity in a rectangular air-lift bioreactor. Industrial & Engineering Chemistry Research, 1999, 38(3): 944-949

25 Jin R C, Zheng P, Mahmood Q, Zhang L. Hydrodynamic characteristics of airlift nitrifying reactor using carrier-induced granular sludge. J Hazard Mater, 2008, 157(2-3): 367-373

PMID

26 Vazquez G, Alvarez E, Navaza J M. Surface tension of alcohol+ water from 20°C to 50°C. Journal of Chemical & Engineering Data, 1995, 40(3): 611-614

27 Marrucci G. A theory of coalescence. Chemical Engineering Science, 1969, 24(6): 975-985

28 Prince M J, Blanch H W. Transition electrolyte concentrations for bubble coalescence. AIChE Journal. American Institute of Chemical Engineers, 1990, 36(9): 1425-1429

29 Tsang Y H, Koh Y H, Koch D L. Bubble-size dependence of the critical electrolyte concentration for inhibition of coalescence. Journal of Colloid and Interface Science, 2004, 275(1): 290-297

PMID

30 Advani S G, Dimitrovová Z. Role of capillary driven flow in composite manufacturing. In: Surface and interface tension: measurement, theory, and applications. Hartland S ed. Surfactant Science Series. New York: Marcel Dekker, Inc, 2004, 119: 263-312

31 Zahradníc J, Kuncová G, Fialová M. The effect of surface active additives on bubble coalescence and gas hold-up in viscous aerated batches. Chemical Engineering Science, 1999, 54 (13-14): 2401-2408

32 Camarasa E, Vial C, Poncin S, Wild G, Midoux N, Bouillard J. Influence of coalescence behavior of the liquid and of gas sparging on hydrodynamics and bubble characteristics in a bubble column. Chemical Engineering and Processing, 1999, 38(4-6): 329-344

33 Jeng J J, Maa J R, Yang Y M. Surface effects and mass transfer in bubble column. Ind Eng Chem Process Des Dev, 1986, 25(4): 974-978

34 Keitel G, Onken U. Inhibition of bubble coalescence by solutes in air/water dispersions. Chemical Engineering Science, 1982, 37(11): 1635-1638

35 Zahradník J, Kuncová G, Fialová M. The effect of surface active additives on bubble coalescence and gas hold-up in viscous aerated batches. Chemical Engineering Science, 1999, 54: 2401-2408

36 Albijanić B V, Ðurić M S, Petrović D L, Tekić M N. Prediction of gas hold-up for alcohol olutions in a draft-tube bubble column. Acta Periodica Technologica, 2006, 37(37): 71-82

37 Šijaćki I M, Čolović R R, Petrović D L, Tekić M N, Ðurić M S. Diluted alcohol solutions in bubble columns and draft tube airlift reactors with a single orifice sparger: experiments and simple correlations. Journal of Chemical Technology & Biotechnology, 2010, 85: 39-49