2. Filtration is commonly the mechanical or physical operation
which is used for the separation of products like solids from
fluids by interposing a medium through which only the fluid
can pass.
The fluid that passes through is called a filtrate.
Filtration is the best established and most versatile method for
removing insoluble from dilute streams like fermentation
broths.
3.
4. Darcy's law is a phenomenological derived constitutive
equation that describes the flow of a fluid through
a porous medium.
Darcy's law is a simple proportional relationship between the
instantaneous discharge rate through a porous medium,
the viscosity of the fluid and the pressure drop over a given
distance.
The total discharge, Q (units of volume per time, e.g., m3/s) is equal to the product of the
intrinsic permeability of the medium, k (m2), the cross-sectional area to flow, A (units of
area, e.g., m2), and the pressure drop (Pb - Pa), (Pascals), all divided by
the viscosity, μ (Pa·s) and the length over which the pressure drop is taking place (m).
General theory of filtration
5. The industrial filtration equipment differs from laboratory
filtration equipment only in the amount of material handled
and in the necessity for low-cost operation.
Fig. Simple laboratory filtration apparatus
6. Filters can also be classified by operating cycle. Filters can
be operated as batch, where the cake is removed after a run,
or continuous, where the cake is removed continuously.
In another classification, filters can be of the gravity type,
where the liquid simply flows by means of a hydrostatic head,
or pressure or vacuum can be used to increase the flow rates.
7. 1. Bed filter
2. Plate-and-frame-filter
3. Leaf Filters
4. Continuous rotary filters
a. Continuous rotary vacuum-drum filter
b. Continuous rotary disk filter
c. Continuous rotary horizontal filter
8. Such filters are useful mainly in cases where relatively
small amounts of solids are to be removed from large
amounts of water in clarifying the liquid.
Fig. Bed Filter
1. BED FILTER
9. 2. PLATE-AND-FRAME-FILTER
The feed slurry is pumped which flows through the duct.
The filtrate flows through the filter cloth and the solids
build up as a cake on the frame side of the cloth. The
filtrate flows between the filter cloth and the face of the
plate through the channels to the outlet.
Fig. Plate-and-frame-filter press
10. 3. Leaf Filters
This filter is useful for many purposes but is not economical
for handling large quantities of sludge or for washing with a
small amount of fresh water. The wash water often channels
in the cake and large volumes of wash water may be needed.
Fig. Leaf Filter
11. 4. Continuous rotary filters
A number of such filters are as follows:
a. Continuous rotary vacuum-drum filter
b. Continuous rotary disk filter
c. Continuous rotary horizontal filter
13. B. CONTINUOUS ROTARY DISK
FILTER
The filter consist of concentric vertical disks mounted on a
horizontal rotating shaft. The filter operates on the same
principle as the vacuum rotary-drum filter. Each disk in
hollow and covered with a filter cloth and is partly submerged
in the slurry.
C. CONTINUOUS ROTARY HORIZONTAL
FILTER
This type is a vacuum filter with the rotating annular filtering
surface divided into sectors. As the horizontal filter rotates, it
successively receives slurry, is washed, is dried, and the cake is
scraped off.
14.
15. slurry is pumped into the trough
The vacuum draws liquid and air through the filter media and out the shaft hence
forming a layer of cake
An agitator is used to regulate the slurry if the texture is coarse and it is settling rapidly
Solids that are trapped on the surface of the drum
washed and dried, removing all the free moisture
16. Microfiltration usually serves as a pre-treatment for other
separation processes such as ultrafiltration, and a post-
treatment for granular media filtration.
The typical particle size used for microfiltration ranges from
about 0.1 to 10 µm.
In terms of approximate molecular weight these membranes
can separate macromolecules generally less than 100,000
g/mol.
17. The filters used in the microfiltration process are specially
designed to prevent particles such as, sediment,
algae, protozoa or large bacteria from passing through a
specially designed filter.
More microscopic, atomic or ionic materials such as water
(H2O), monovalent species such as Sodium (Na+) or Chloride
(Cl-) ions, dissolved or natural organic matter, and
small colloids and viruses will still be able to pass through the
filter.
18. Sparks, T. (2012) Solid-Liquid Filtration - A Users’ Guide to Minimizing
Costs and Environmental Impact; Maximizing Quality and Productivity,
Elsevier.
Haug, G. (1999) Aspects of Rotary Vacuum Filter Design & Performance,
Eagle-Picher Minerals Inc.
Crittenden, J, Trussell, R, Hand, D, Howe, K & Tchobanoglous, G.
2012, Principles of Water Treatment, 2nd edn, John Wiley and Sons, New
Jersey. 8.1.
Perry, RH & Green, DW, 2007. Perry's Chemical Engineers' Handbook, 8th
Edn. McGraw-Hill Professional, New York. p. 2072.
Baker, R 2000, Microfiltration, in Membrane Technology and Applications,
John Wiley & Sons Ltd, California. p. 279
Kenna,E & Zander, A 2000, Current Management of Membrane Plant
Concentrate, American Waterworks Association, Denver. p.14
Perry, RH & Green, DW, 2007. Perry's Chemical Engineers' Handbook, 8th
Edn. McGraw-Hill Professional, New York. p 2072-2100
Seadler ,J & Henley, E 2006, Separation Process Principles, 2nd Edn, John
Wiley & Sons Inc. New Jersey. p.501
