Thickeners operating layers

A typical thickener has three operating layers clarification, zone-settling, and compression. Frequently, the feed is contained in the zone-settling layer which theoretically eliminates the need for the clarification zone because the particles would not escape through the interface. In practice, however, the clarification zone provides a buffer for fluctuations in the feed and the sludge levels. 

The only possible problem of decreasing the feed rate was whether the thickening of gel layer and concentration polarization due to the slow juice speed would raise the osmotic pressure on the membrane surface as high as the operating pressure before the bulk concentration reaches the required value. 

Associative thickeners increase the viscosity of the paint by interacting with other paint ingredients through bridging of particles (surface to surface) or interaction of adsorbed layers. The interactions are assumed to be through hydrophobic forces. The operative mechanism is illustrated in Figure 5.9. Important groups in this class are associative acrylic thickeners, associative cellulose ethers and hydrophobically modified ethoxylated urethanes (HEUR). 

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