Prediction of the gas hold-up in a large-diameter bubble column with liquid mixtures and electrolytes

- A correlation for predicting the gas hold-up in bubble columns is proposed.
- The proposed correlation is applied at low and at high gas velocities.
- The dependence of the gas hold-up on concentration is considered.
- The enhancement due to the presence of electrolytes is taken into account.

Many correlations are available in the literature for computing the gas hold-up in bubble columns, mainly in pure liquids. Contrarily, very few works deal with the gas hold-up in liquid mixtures, giving different opinions about the successful application of Andrew's dynamic surface tension model. This work further investigates this topic using more recent gas hold-up data presented in a previous work for the binary mixture comprising monoethylene glycol and water and measured for a large-diameter bubble column, which differs from the equipment used in the other few works that have pointed out the unusual behavior of the gas hold-up in binary liquid mixtures. The correlation proposed for representing the experimental data on the basis of the dynamic surface tension theory has been applied in the entire range of gas superficial velocities (0.004-0.20 m/s) and it has been also generalized to predict the gas hold-up enhancement due to the presence of electrolytes. The results suggest that the dynamic surface tension model allows to reproduce the experimental gas hold-up data in a qualitative way, but a quantitative agreement is still lacking since the maximum frothing ability has been experimentally observed for a monoethylene glycol concentration lower than that predicted by Andrew's theory.

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