Monitoring of the bubble columns hydrodynamics by recurrence quantification data analysis

Hydrodynamics of bubble column in the presence of different collectors was investigated by recurrence quantification analysis (RQA). By measuring the local pressure fluctuations of the gas-liquid bubble column by a piezo-resistive sensor and transforming the data to the state space, the recurrence plots were generated. Then, using the RQA, recurrence rate, determinism, and entropy of the plot were calculated. The RQA allows characterizing the flow regime and investigating the effect of adding various collectors, such as amine and ester, in square bubble columns. The results showed that determinism and entropy are sensitive parameters to detect the hydrodynamic changes in the bubble column. Furthermore, the transition range from homogeneous to heterogeneous regime was detected for tap water-air (4.4-5 cm/s), 50 ppm amine aqueous solution-air (4.4-5 cm/s), and ester aqueous solution-air (2.5-3.5 cm/s) systems. By examining the effect of adding collectors, it was found that entropy performs much better in detecting the changes in the hydrodynamics of the bubble column. For example, by adding 5 ppm ester to water, entropy changed 2.5 times more than determinism. As a result, entropy can be considered as the proper recurrence parameter for investigating the hydrodynamics of bubble columns. (c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.