mechanism of filtration, surface and depth filters

this presentation is about the filtration process and its types.

1. Filtration
Prepared By:
Saqib Salman
(16103123-041)
Department of Chemical Engineering
University of Gujrat,
Gujrat, Pakistan.

2. Introduction
Filtration may be defined as the separation of
solids from liquids by passing a suspension through
a permeable medium which retains the particles.
Figure 1. Schematic diagram of filtration system

3. The fine apertures necessary for filtration are provided
 by fabric filter cloths,
 by meshes and screens of plastics or metals,
 by beds of solid particles.
In some cases, a thin preliminary coat of cake, or of other fine
particles, is put on the cloth prior to the main filtration process.

4. Types of filtration
1. Surface filters
2. Depth filters

5. 1.Surface filters
used for cake filtration in which the solids are
deposited in the form of a cake on the up-stream
side of a relatively thin filter medium.
Figure2. Mechanism of cake filtration

6. 2.Depth filters
used for deep bed filtration in which particle
deposition takes place inside the medium and cake
deposition on the surface is undesirable.
Figure 3. Mechanism of deep bed filtration

7. The fluid passes through the filter medium, which
offers resistance to its passage, under the influence
of a force which is the pressure differential across
the filter.
rate of filtration = driving force/resistance

8. Filtration Media:
It can be considered as the heart of the filtration device
or machine.
Provides adequate porosity capable of passing liquid
through, while retaining solids
Medium is characterized by its filtration properties of
permeability and retention.
It can be
•Natural
•Synthetic or glass
•Woven cloth
•Paper
•Ceramic

9. Factor affected on filtration
•Pressure drop ( ∆P )
•Area of filtering surface ( A )
•Viscosity of filtrate ( v )
•Resistance of filter cake ( α )
•Resistance of filter medium ( R
m
)
•Properties of slurry ( μ , ฯฯฯ )

10. rate of filtration = driving force/resistance
-(DP) or
Pressure
drop
Filter cake (a)
Filter medium (R
m
)
Viscosity (m)