Mass transfer estimation for bubble column scale up

Abstract The productivity of a bubble column reactor (BCR) critically depends upon gas-liquid mass transfer coefficient, k L a . The prediction of k L a as function of design and operating conditions is central to BCR scale up. A large number of researchers have successfully characterized k L a experimentally in terms of superficial gas velocity, U sg using the power law relation k L a = α U sg β , with α , β as fit parameters. We probe the applicability of such correlations to the design of a scaled up BCR, which differs from laboratory BCR in two important aspects: (i) the scale of operation, which can be O ( 10 2 - 10 3 ) times larger, and (ii) the type of sparger used. To this end, experiments were performed with air and water in a pilot scale ( D C = 1.6 m diameter) BCR using a coarse bubble sparger. We found that the existing correlations do, indeed, describe k L a over a wide range of BCR sizes, suggesting that these correlations are fairly scale insensitive. However, the correlations provide no means to capture the role of sparger explicitly. We cast our experimental k L a values in terms of a mass transfer efficiency and independently recover the power law relation with β = 1 . We suggest that the role of sparger design can be incorporated in the definition of α through the well-documented sparger efficiency factors. The α and β estimates thus obtained are in good agreement with the literature.