Control of Surface Properties and Efficiency of Some Antifoams Used in Beet Sugar Processing

摘要

In the sugar factory, foam formation occurs at all stages of processing, beginning with beet washing. One of the main problem ares in this respect is that of diffusion extraction. Numerous problems are associated with foam formation, such as extractor clogging, extraction yield decrease and sugar loss due to vat overflow. To prevent these problems, antifoams are injected. However, the formulas of such technical aids are complex and generally patented. Thus, the user of antifoams has to use the services of suppliers who keep secret their formula. In this work we have compared different formulas of antifoams by studying their mechanism of action and optimizing the efficient doses.rnRelative efficacy of six samples of antifoams was determined as a function of concentration and temperature. It was shown that efficacy increases with concentration and shows a threshold. The effect of temperature resides in the need that antifoams are added at a temperature above the turbidity point. Likewise, antifoams were classified as a function of their hydrophobicity and efficacy at normal temperature. It was shown that efficacy increases with hydrophobicity. The more efficient an antifoam, the slower is its adsorption at the air/liquid interface. A mechanism for trapping of juice surface active molecules by antifoams is proposed.rnFinally, adsorption kinetics was studied at high temperature for antifoams quickly adsorbed at normal temperature. It was found that increasing the temperature facilitates the adsorption of antifoams at the interface. Such an adsorption is the more important the more efficient the antifoam is at normal temperature. Decrease in activation energy for the adsorption of antifoam from subsurface to interface was proposed as a possible explanation of antifoam behavior at interfaces.