Experimental investigation and its analysis of gas holdup in a three-phase counter-current microstructured bubble column

Abstract

The present work investigates the gas holdup in a three-phase counter-current microstructured bubble column with and without the presence of surfactant. The coal (specific gravity 1.4) was taken to prepare slurry (a mixture of water and coal) and Methyl Isobutyl Carbinol (MIBC) was used as a surfactant. The effects of the dispersed phase $(\mathrm{i}.\mathrm{e}.,\mathrm{ }\text{air},\mathrm{ }{u}_{\text{sg}}=\mathrm{ }0.011\mathrm{ }-\mathrm{ }0.075\mathrm{ }\mathrm{m}/\mathrm{s})$ and continuous phase $(\mathrm{i}.\mathrm{e}.,\mathrm{ }\text{slurry},\mathrm{ }{u}_{\text{sg}}=\mathrm{ }0.011\mathrm{ }-\mathrm{ }0.075\mathrm{ }\mathrm{m}/\mathrm{s})$ velocity, solid loading $(\mathrm{i}.\mathrm{e}.,\mathrm{ }0.5\mathrm{ }-\mathrm{ }3.0\mathrm{ }\text{wt}\%),$ and solid size $(\mathrm{i}.\mathrm{e}.,\mathrm{ }63.01\mathrm{ }-\mathrm{ }517.0\text{ μm})$ on gas holdup are studied. The result shows that the gas holdup is highly dependent on the operating variables and the solid loading, but only to a small extent on the size of the particles. The gas holdup is analyzed with a slip velocity model. The maximum gas holdup in the column is found to be 38.570% and 33.195% in the presence and absence of the surfactant, respectively. It has been found that increasing the concentration of solids reduces gas holdup. Moreover, increasing particle size and dispersed phase and continuous phase velocity increases gas holdup. A novel correlation has been developed to predict the gas holdup and slip velocity model parameters. Gas holdup data from the available literature and the current experimental values were compared to the recommended correlation. The results of the study show that the recommended correlations give a precise prediction of experimental values in the error range of ± 20%.

Keywords:

• Gas holdup
• particle size
• particle concentration
• slip velocity model
• slurry bubble column

Acknowledgment

The authors are thankful to Central Instrument Facility (CIF) of IIT Guwahati for allowing us to capture the image of the particles using Field Emission Scanning Electron Microscope (FESEM).