This document discusses filtration and cake filtration principles. Filtration is the separation of solids from a liquid suspension using a porous medium. In cake filtration, the suspended solids build up on the filter medium over time, forming a thicker cake with higher resistance. As the cake builds, the filtration rate decreases unless more pressure is applied. Common cake filters include filter presses, belt filters, and various types of vacuum filters that use a building cake to separate solids from liquids.

1. Filtration, Cake filters &
Principles Of Cake Filtration

2. Content
• Filtration
• Principle of cake filtration
• Cake filters
• Types of filters
Filtration, Cake filters & Principles Of Cake Filtration

3. FILTERATION
The separation of solids from a suspension in a liquid with the
help of a porous medium or screen which retains the solids and
allows the liquid to pass is termed filtration.

4. Filtration
In the laboratory, the suspension is poured
into a conical funnel fitted with a filter paper.
In the industrial equivalent, difficulties are
encountered in the mechanical handling of
much larger quantities of suspension and
solids.
A thicker layer of solids has to form and, in
order to achieve a high rate of passage of
liquid through the solids, higher pressures
are needed, and a far greater area has to be
provided.

5.  Factors affecting rate of filtration:
a) Pressure drop across the feed inlet and side of filter
medium.
b) Area of the filtering surface.
c) Viscosity of the filtrate.
d) Resistance of the filter medium.
e) Resistance of the filter cake.
 Types of filtration:
1) Constant pressure filtration
2) Constant rate filtration

6. Principle of filtration

7. Principles Of Cake Filtration
 In cake filtration, the feed to be handled is termed as slurry,
the bed of deposited solid on a porous membrane is termed
as cake, and the clear liquid leaving the filter medium is
termed as filtration.
 A typical cake filtration operation is shown in fig.
 During the initial period of flow, solid particles are trapped
within the pores of a medium forming the true filter medium.
 The liquid passes through the bed of the solid and through
the filter medium.
 In the early stage of filtration, the rate of filtration is high.

8.  This is due to the fact that as the cake gradually builds upon
the medium, the resistance to flow progressively increases.
 As the thickness of the cake increases
• resistance to flow of filtrate increases
• rate of filtration gradually decreases.
 If rate is maintained to be constant then pressure difference
driving force (-P) will increase.

9. Type of Filter
• Cake Filter
• Clarifying Filter
• Cross Flow
• Ultra Filter

10. Cake Filter
• A filter cake is formed by the substances that are retained on
a filter .
• The filter cake grows in the course of filtration, becomes
"thicker" as particulate matter is being retained.
• With increasing layer thickness the flow resistance of the filter
cake increases
• After a certain time of use the
filter cake has to be removed
from the filter,
e.g. by back flushing.
Filter cake

11. Examples of Cake Filters
• Filter presses
• Belt filters
• Vacuum filters:
- Rotary vacuum belt filters
- Rotary vacuum precoat filters
- Vacuum disk filters

12. Thank You