Optimisation of defoamer in a bio-reactor

Mangudu, James
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The success rate in the use of defoamers for controlling foam lies in finding the optimal concentration of defoamer for each foam type. Due to the dynamic nature of the foaming conditions in bio-reactors, using one concentration of defoamer across all foaming conditions may not be efficient. Where the plant design requires the use of defoamers for foam control, finding the right defoamer concentration ideal for each foam type becomes key. The objective of this study was to examine the following questions: first, can a more dilute form of Zeta Airspel 300® defoamer achieve complete foam knock-down and lengthy foam stay down times in the bio-reactor? And second, can this be achieved at a lesser cost than using 100% concentrated defoamer. To examine these questions, two sets of experiments were performed, batch experiments and plant trials, with defoamer concentrations ranging from 1%-100%. Defoamer samples with 40% concentration and above managed to completely reduce foam in both the batch experiment and in the bio-reactor. The rates of foam decay were faster with increase in defoamer concentration and foam suppression times were lengthier with increase in defoamer concentration. The economic evaluation of the plant trial results showed that 90% defoamer concentration was the least costly option of all. This discovery suggests that different defoamer concentrations can be used optimally depending on foaming conditions present in the bio-reactor at each given time. Future studies should focus on conducting longer plant trials during periods of different foaming conditions to be able to develop a model that predicts the most cost effective defoamer concentration for each particular foam type.
A research report submitted to the Faculty of Engineering and the Built Environment, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2017
Mangundu, James (2017) Optimisation of defoamer in a bio-reactor, , University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/24961>