Tiller Points

In pressure cake filtration, it is normally expected to receive higher filtration rate and cake solid content (called solidosity) by increasing the operating pressure.

This is true for incompressible and moderately compactible material. However, for highly compactible materials, such as flocculated, fragile, or very fine particles, the filtration rate and average cake solidosity will plateau at certain values even when pressure continuously increases as shown in the following figure.

The critical pressure drop beyond which there is little effect of pressure on either the flow rate or average cake solidosity is defined as the Tiller Point. This is to honor Prof. Frank M. Tiller who was called the father of the modern cake filtration theory and was the first one to explain this phenomena from fundamental theory. . In practice, Tiller Point is defined as the pressure when filtration rate reached 90% of its maximum value.

In operation, when Tiller Point is reached, there is no need to increase pressure in order to increase the filtration rate or cake average solidosity. Mechanical expression should be applied for further solidosity increasing.

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