Measurement of gas hold-up in bubble columns from low frequency acoustic emissions

This paper demonstrates a novel method of global gas hold-up estimation in a laboratory scale bubble column using acoustic emissions from within the column, which are caused by bubble generation. Bubble formation excites the column to resonate at its natural frequencies; these frequencies are determined by the vessel dimensions. Peaks in the 0-1000 Hz range of the acoustic spectrum were observed and identified as the column resonance frequencies. Measured changes in resonance frequencies for a range of global gas hold-ups (up to 20%) correlated well with theory. This method of global gas hold-up monitoring should be particularly useful for systems where measurements of changes in liquid height are not possible. (C) 2002 Elsevier Science B.V. All rights reserved.