Effect of contaminants on mass transfer coefficients in bubble column and airlift contactors

• Published in: Chemical engineering science Vol. 58; no. 8; pp. 1431 - 1440
• Main Authors: Vasconcelos, J.M.T, Rodrigues, J.M.L, Orvalho, S.C.P, Alves, S.S, Mendes, R.L, Reis, A
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2003; Elsevier
• Subjects: Airlift; Applied sciences; Bubble; Bubble column; Chemical engineering; Exact sciences and technology; Interface; Mass transfer; Reactors; Surfactant; Bubble; Surfactant; Mass transfer; Interface; Airlift; Bubble column; Gas liquid; Airlift reactor; Mass transfer coefficient; Theoretical study; Oxygen transfer; Volumetric mass transfer coefficient; Experimental study; Modeling
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/S0009-2509(02)00675-9

In this work, the effects of surface-active contaminants on mass transfer coefficients k L a and k L were studied in two different bubble contactors. The oxygen transfer coefficient, k L , was obtained from the volumetric oxygen transfer coefficient, k L a, since the specific interfacial area, a, could be determined from the fractional gas holdup, ε, and the average bubble diameter, d 32. Water at different heights and antifoam solutions of 0.5– 100 ppm were used as working media, under varying gas sparging conditions, in small-scale bubble column and rectangular airlift contactors of 6.7 and 0.85×10 −3 m 3 capacity, respectively. Both the antifoam concentration and the bubble residence time were shown to control k L a and k L values over a span of almost 400%. A theoretical interpretation is proposed based on modelling the kinetics of single bubble contamination, followed by sudden surface transition from mobile to rigid condition, in accordance with the stagnant cap model. Model results match experimental k L data within ±30%.