Some Design Considerations and Factors Influencing Behavior

2 Some Design Considerations and Factors Influencing Behavior 

One of the problems in applying foam-breaking cyclones is that it is difficult to quantitatively predict, a priori, just how well they will perform in practice. 

If the liquid phase viscosity is too high (greater than approximately 50 cp, for example), the dispersed foam bubbles may not respond well to the applied centrifugal field within the cyclone. Likewise, if the bubbles are too small or form a micro-dispersion , the separation will be ineffective. 

On the other hand, the production or process engineer often is only interested in knowing if his or her rniit is going to have a foaming problem or not— yes or no Whether the separation efficiency is 99% or 99.8% is of less consequence. Under these conditions, experience with similar processes can be extremely valuable and, if such experience is not available in-house , the equipment vendor s experience may prove very helpful. 

As with all foam-related problems, sm-face tension and surface chemistry play an important role with defoaming cyclone-type separators. Yet, in most cases of practical interest, our understanding of the coalescence process is poor. This is because many industrially important processes for which foam is a problem are characterized by heavy, dirty feeds consisting of a complex heterogeneous blend of gas, oil, water, dissolved salts and, often, solids. Operating pressures and temperature may also be far removed from ambient conditions or from that which can be readily studied in a laboratory setting. 

---