This document discusses various types and mechanisms of filtration. It begins by defining filtration as the process of separating solids from fluids by passing them through a porous medium. Some key applications include producing sterile drugs and liquid oral formulations. The main types of filtration are surface, depth, and cake filtration. Surface filtration relies on pore size to retain solids, while depth filtration relies on particle entanglement within pores. Cake filtration uses a woven cloth to form a particle bed. Factors like particle size and pressure influence the filtration rate. Common equipment includes plate and frame presses and filter leaves.

1. FILTRATION
Presented by
Dr.K.KAVITHA
ASST.PROFESSOR
UNIVERSITY COLLEGE OF ENGINEERING
BIT CAMPUS, ANNA UNIVERSITY
TIRUCHIRAPPALLI

2. It may be defined as a process of separation of
solids from a fluid by passing the same
through a porous medium that retains the
solids, but allows the fluid to pass through.

3. APPLICATIONS
• PRODUCTION OF STERILE DRUGS.
• PRODUCTION OF BULK DRUGS.
• PRODUCTION OF LIQUID ORAL
FORMULATIONS.
• EFFLUENT AND WASTE WATER
TREATMENT.

4. MECHANISM OF FILTRATION
• STRAINING.
• IMPINGEMENT.
• ENTANGLEMENT.
• ATTRACTIVE FORCES.

5. TYPES OF FILTRATION
• SURFACE (SCREEN) filtration.
• DEPTH filtration.
• CAKE filtration.

6. SURFACE FILTRATION
• IT IS A SCREENING ACTION BY WHICH
PORES OR HOLES OF THE MEDIUM
PREVENT THE PASSAGE OF SOLIDS.
• THE MECHANISMS, STRAINING AND
IMPINGEMENT ARE RESPONSIBLE
FOR THIS FILTRATION.

7. DEPTH FILTRATION
• IN THIS PROCESS, SLURRY
PENETRATES TO A POINT WHERE THE
DIAMETER OF SOLID IS GREATER
THAN THAT OF THE TORTUOS VOID
OR CHANNEL.
• IT IS AIDED BY THE MECHANISM
ENTANGLEMENT.

8. DIFFERENCES BETWEEN SURFACE
AND DEPTH FILTRATIONS
• SURFACE FILTRATION
• SIZE OF THE PARTICLES
RETAINED IS SLIGHTLY
HIGHER THAN THE MEAN
PORE SIZE OF MEDIUM
• MECHANICAL STRENGTH IS
LESS, UNLESS IT IS MADE
OF STAINLESS STEEL
• IT HAS LOW CAPACITY
• SIZE OF THE PARTICLES
RETAINED IS PREDICTABLE
• EQUIPMENT IS EXPENSIVE
BECAUSE IT SHOULD
REQUIRE ANCILLARY
EQUIPMENT
• EXAMPLE IS CELLULOSE
MEMBRANE FILTER
• DEPTH FILTRATION
• SIZE OF THE PARTICLES
RETAINED IS MUCH
SMALLER THAN THE PORES
THROUGH WHICH FLUID
PASSES
• MECHANICAL STRENGTH IS
HIGH
• IT HAS HIGH CAPACITY
• SIZE OF THE PARTICLES
RETAINED IS LESS
PREDICTABLE
• CHEAPER BECAUSE
ANCILLARY EQUIPMENT IS
NOT REQIRED
• EXAMPLES ARE CERAMIC
AND SINTERED FILTERS

9. CAKE FILTRATION
• A FILTER CONSISTS OF A COARSE
WOVEN CLOTH THROUGH WHICH A
CONCENTRATED SUSPENSION OF
RIGID PARTICLES IS PASSED SO THAT
THEY BRIDGE THE HOLES AND FORM
A BED.

10. THEORIES OF FILTRATION
• POISEUILLES EQUATION.
• DARCYS EQUATION.
• KOZENY-CARMAN EQUATION.

11. POISEUILLES EQUATION
• HE CONSIDERED THAT FILTRATION IS
SIMILAR TO THE STREAMLINE FLOW OF A
LIQUID UNDER PRESSURE THROUGH
CAPILLARIES. EQUATION IS:
• V = Pr4 / 8Ln
• V = rate of flow , i.e., volume of liquid flowing
in unit time, m3/s(1/s)
• P = pressure difference across the filter,Pa
• r = radius of the capillary in the filter bed, m
• L = thickness of the filter cake (capillary length),
• n = viscosity of the filterate, pa.s

12. DARCYS EQUATION
• POISEUILLES LAW ASSUMES THAT THE
CAPILLARIES FOUND IN FILTER ARE HIGHLY
IRREGULAR AND NON-UNIFORM.
• THEREFORE,IF THE LENGTH OF A CAPILLARY IS
TAKEN AS THE THICKNESS OF A BED, A
CORRECTION FACTOR FOR RADIUS IS APPLIED SO
THAT THE RATE EQUATION IS CLOSELY
APPROXIMATED AND SIMPLIFIED.EQUATION IS :
• V = KAP/nL
• K = PERMEABILITY COEFICIENT OF THE CAKE ,M2.
• A = SURFACE AREA OF THE POROUS BED (FILTER
MEDIUM), M2.

13. KOZENY-CARMAN EQUATION
• POISEUILLE’S EQUATION IS MADE APPLICABLE TO
POROUS BED, BASED ON A CAPILLARY TYPE
STRUCTURE BY INCLUDING ADDITIONAL
PARAMETERS.
• THUS THE RESULTANT EQUATION, WHICH IS
WIDELY USED FOR filtration IS KOZENY-CARMAN
EQUATION
• V = A/NS2 . P/KL. 3/(1- )2
•  = POROSITY OF THE CAKE (BED)
• S = SPECIFIC SURFACE AREA OF A PARTICLES
COMPRISING THE CAKE, M2/M3
• K = KOZENY CONSTANT

14. FACTORS INFLUENCING filtration
• SOME OF THE FACTORS INFLUENCING THE filtration ARE.
1. PROPERTIES OF THE LIQUIDS – DENSITY, VISCOSITY AND
CORROSIVENESS
2. PROPERTIES OF THE SOLIDS – PARTICLE SHAPE,
PARTICLE SIZE, PARTICLE CHARGE, DENSITY, PARTICLE
SIZE DISTRIBUTION, RIGIDITY (OR) COMPRESSIBILITY OF
THE SOLID UNDER PRESSURE AND TENDENCY OF
PARTICLE TO FLOCCULATE (OR) ADHERE TOGETHER.
3. PROPORTION OF SOLIDS IN THE SLURRY – RATE AT WHICH
THE FILTER CAKE IS FORMED, ESPECIALLY IN THE EARLY
STAGES OF THE filtration.
4. OBJECTIVES – WHETHER THE SOLIDS OR THE LIQUID OR
BOTH ARE TO BE COLLECTED.
5. TEMPERATURE OF THE SUSPENSION.

15. OTHER FACTORS
• SURFACE AREA OF THE FILTER MEDIUM .
• PRESSURE DROP ACROSS THE FILTER
MEDIUM.
1. GRAVITY .
2. APPLYING PRESSURE.
3. REDUCING PRESSURE.
4. CENTRIFUGAL FORCE.
• VISCOSITY OF FILTERATE.

16. FILTER MEDIA
• THE FILTER MEDIUM ACTS AS A MECHANICAL SUPPORT
FOR THE FILTER CAKE AND IS ALSO RESPONSIBLE FOR
THE COLLECION OF SOLIDS .
• CHARACTERSTICS : FILTER MEDIUM SHOULD HAVE THE
FOLLOWING CHARACTERSTICS
1. IT SHOULD HAVE SUFFICIENT MECHANICAL STRENGTH.
2. IT MUST BE INERT, FOR EXAMPLE, IT SHOULD NOT SHOW
CHEMICAL OR PHYSICAL INTERACTION.
3. IT SHOULD NOT ABSORB THE DISSOLVED MATERIAL.
4. IT SHOULD ALLOW THE MAXIMUM PASSAGE OF LIQUID,
WHILE RETAINING THE SOLIDS. IT MEANS THAT IT MUST
OFFER LOW RESISTANCE TO FLOW. THE RESISTANCE
OFFERED BY THE FILTER MEDIUM IS NOT SIGNIFICANT IN
LARGE SCALE OPERATIONS AND CAN BE NEGLECTED.

17. MATERIALS USED IN FILTER
MEDIA
1. WOVEN MATERIALS SUCH AS FELT OR
CLOTH.
2. PERFORATED STEEL METAL.
3. BED OF GRANULAR SOLID BUILT UP ON A
SUPPORTING MEDIUM.
4. PRE-FABRICATED POROUS SOLID UNIT.
5. MEMBRANE FILTER MEDIA;
• SURFACE TYPE CARTRIDGES.
• DEPTH TYPE CARTRIDGES.

18. FILTER AIDS
• THEY FORMS A SURFACE DEPOSIT WHICH
SCREENS OUT THE SOLIDS AND ALSO
PREVENTS THE PLUGGING OF THE SUPPORTING
FILTER MEDIUM.
• CHARACTERSTICS : THE IMPORTANT
CHARACTERSTICS OF THE FILTER AIDS ARE :
1. CHEMICALLY INERT TO THE LIQUID BEING
FILTERED AND FREE FROM IMPURITIES
2. LOW SPECIFIC GRAVITY, SO THAT FILTER AIDS
REMAINS SUSPENDED IN LIQUID
3. POROUS RATHER THAN DENSE, SO THAT
PREVIOUS CAKE CAN BE FORMED
4. RECOVERABLE

19. HANDLING OF FILTER AIDS
• FILTER AIDS ARE MOSTLY USED FOR
CLARIFICATION PROCESSES, i.e; WHERE
SOLIDS ARE DISCARDED. DIFFERENT
FLOW RATES CAN BE ACHIEVED
DEPENDING ON THE GRADE OF THE AIDS.
1. LOW FLOW RATE (FINE SOLIDS) – FINE
GRADE FILTER AIDS – MAINLY INTNDED
FOR CLARITY.
2. FAST FLOW RATE (COARSE SOLIDS) –
COARSE GRADE – ACCEPTABLE
FILTERATE .

20. EXAMPLES OF FILTER AIDS
• KEISELGUHR
• TALC
• CHARCOAL
• ASBESTOS
• PAPER PULP
• BENTONITE
• FULLERS EARTH

21. CLASSIFICATION OF
FILTRATION EQUIPMENT
• EQUIPMENT ARE CLASSIFIED BASED ON THE
APPLICATIONS OF EXTERNAL FORCE.
1. Pressure filters.
2. Vaccum filters.
3. Centrifugal filters.
• CLASSIFICATION BASED ON THE OPERATION OF THE
FILTRATION.
1. Continuos filtration.
2. Dis – continuous filtration.
• CLASSIFICATION BASED ON THE NATURE OF FILTRATION.
1. Cake filters.
2. Clarifying filters.
3. Cross – flow filters.

22. PLATE AND FRAME FILTER
PRESS
• PRINCIPLE : THE MECHANISM IS SURFACE filtration.
THE SLURRY ENTERS THE FRAME BY PRESSURE
AND FLOWS THROUGH THE FILTER MEDIUM.
• THE FILTERATE IS COLLECTED ON THE PLATES
AND SENT TO THE OUTLET.
• A NUMBER OF FRAMES AND PLATES ARE USED SO
THAT SURFACE AREA INCREASES AND
CONSEQUENTLY LARGE VOLUMES OF SLURRY
CAN BE PROCESSED SIMULTANEOUSLY WITH OR
WITHOUT WASHING.

23. CONSTRUCTION -1
• THE FILTER PRESS IS MADE OF TWO TYPES OF
UNITS. THEY ARE :
1. PLATES.
2. FRAMES.
• THESE ARE USUALLY MADE OF ALUMINIUM
ALLOY. SOME TIMES, THESE ARE ALSO
LACQUERED FOR PROTECTION AGAINST
CORROSIVE CHEMICALS AND MADE SUITABLE
FOR STEAM STERILISATION
• FRAME CONSIST AN OPEN SPACE INSIDE
WHEREIN SLURRY RESERVOIR IS MAINTAINED
FOR filtration AND AN INLET TO RECEIVE THE
SLURRY.

24. CONSTRUCTION - 2
• THE PLATE HAS A STUDDED OR GROVED SURFACE TO
SUPPORT THE FILTER CLOTH AND AN OUTLET.
• THE FILTER MEDIUM (USUALLY CLOTH) IS INTERPOSED
BETWEEN PLATE AND PLATES.
• FRAMES OF DIFFERENT THICKNESSES ARE AVAILABLE.IT IS
SELECTED BASED ON THE THICKNESS OF THE CAKE
FORMED DURING filtration.
• PLATE, FILTER MEDIUM, FRAME, FILTER MEDIUM AND PLATE
ARE ARRANGED IN SEQUENCE AND CLAMPED TO A
SUPPORTING STRUCTURE.
• A NUMBER OF PLATES AND FRAMES ARE EMPLOYED SO
THAT filtration AREA IS AS LARGE AS NECESSARY.
• CHANNALS FOR THE SLURRY INLET AND FILTERATE OUTLET
CAN BE ARRANGED BY FITTING EYES TO THE PLATES AND
FRAMES.THSES JOIN TOGETHER TO FORM A CHANNAL.

26. WORKING
• WORKING OF THE PLATE AND
FRAME PRESS PROCESS CAN BE
DESCRIBED IN TWO STEPS. THEY
ARE :
1. FILTRATION OPERATION.
2. WASHING OPERATION.

27. 1. FILTRATION OPERATION
• SLURY ENTERS THE FRAME FROM THE FEED CHANNAL AND
PASSES THROUGH THE FILTER MEDIUM ON TO THE SURFACE.
• THE SOLIDS FROM A FILTER CAKE AND REMAIN IN THE FRAME.
• THE THICKNESS OF THE CAKE IS HALF OF THE FRAME THICKNESS,
BECAUSE ON EACH SIDE OF THE FRAME filtration OCCURS.
• THUS TWO FILTER CAKS ARE FORMED, WHICH MEET EVENTUALLY
IN THE CENTER OF THE FRAME.
• IN GENERAL, THERE WILL BE AN OPTIMUM THICKNESS OF THE
FILTER CAKE FOR ANY SLURRY, DEPENDING ON THE SOLID
CONTENT IN THE SLURRY AND THE RESISTANCE OF THE FILTER
CAKE.
• AS filtration PROCEEDS, THE RESISTANCE OF THE CAKE INCREASES
AND THE filtration RATE DECREASES.
• AT A CERTAIN POINT IT IS PREFERABLE TO STOP THE PROCESS
AND START THE NEW ONE.

28. 2.WASHING OPERATION
• PROCEDURE FOR WASHING THE PRESS ARE AS FOLLOWS
:
1. filtration PROCEEDS IN THE ORDINARY WAY UNTIL THE
FRAMES ARE FILLED WITH CAKE.
2. TO WASH THE FILTER CAKE, THE OUTLETS OF THE
WASHING PLATES ARE CLOSED.
3. WASH WATER IS PUMPED INTO THE WASHING CHANNAL.
THE WATER ENTERS THROUGH THE INLETS ON TO THE
SURFACE OF THE WASHING PLATES.
4. WATER PASSES THROUGH THE FILTER CLOTH AND
ENTERS FRAME WHICH CONTAINS THE CAKE. THEN
WATER WASHES THE CAKE, PASSES THROUGH THE
FILTER CLOTH AND ENTERS THE PLATE DOWN THE
SURFACE.
5. FINALLY WASHED WATER ESCAPES THROUGH THE
OUTLET OF THE PLATE.

30. USES OF FILTER PRESS
1. FILTER SHEETS COMPOSED OF
ASBESTOS AND CELLULOS ARE CAPABLE
OF RETAINING BACTERIA, SO THAT
STERILE FILTERATE CAN BE OBTAINED BY
STERILISING THE FILTER MEDIUM AND
PRESS PREVIOUSLY
2. USUALLY STEAM IS PASSED THROUGH
THE ASSEMBLED UNIT OF STERILISATION.
3. HEATING/COOLING COILS ARE
INCORPORATED IN THE PRESS SO AS TO
MAKE IT SUITABLE FOR THE filtration OF
VISCOUS LIQUIDS.

31. ADVANTAGES
• EFFICIENT WASHING OF THE CAKE IS POSSIBLE.
• CONSTRUCTION OF FILTER PRESS IS VERY
SIMPLE AND A VARIETY OF MATERIALS CAN BE
USED. THEY ARE :
1. CAST IRON
2. BRONZE
3. STAINLESS STEEL
4. HARD RUBBER OR PLASTICS
5. WOOD
• ABOUT 2000 KILOPASCALS CAN BE NORMALLY
USED.
• IT PRODUCES DRY CAKE IN THE FORM OF SLAB.

32. DISADVANTAGES
1. IT IS A BATCH FILTER, SO THERE IS A
GOOD DEAL OF ’ DOWN-TIME’, WHICH IS
NON PROTECTIVE.
2. IT IS AN EXPENCIVE FILTER.
3. THE OPERATION INVOLVED IS CRITICAL.
4. IT IS USED FOR SLURRIES CONTAINING
LESS THAN 5% SOLIDS.
5. HIGH COSTS MAKE IT IMPERATIVE THAT
THIS FILTER PRESS IS USED FOR
EXPENSIVE MATERIALS.

33. FILTER LEAF
• PRINCIPLE :
1. IT IS AN APPARATUS CONSISTING OF A LONGITUDINAL
DRAINAGE SCREEN COVERED WITH A FILTER CLOTH.
2. THE MECHANISM IS SURFACE filtration AND ACTS AS SIEVE
OR STRINER.
3. VACUUM OR PRESSURE CAN BE APPLIED TO INCREASE
THE RATE OF filtration.
• CONSTRUCTION :
1. IT CONSISTS OF A NARROW FRAME ENCLOSING A
DRAINAGE SCREEN OR GROOVED PLATE.
2. FRAME MAY BE OF ANY SHAPE, CIRCULAR, SQUARE OR
RECTANGULAR.
3. THE WHOLE UNIT IS COVERED WITH FILTER CLOTH.
4. THE OUTLET FOR THE FILTERATE CONNECTS TO THE
INTERIOR OF THE FRAME THROUGH SUCTION.

35. WORKING
1. FILTER LEAF IS IMMERSED IN THE SLURRY.
2. VACUUM FILTER IS CONNECTED TO FILTERATE OUTLET.
3. SLURRY PASSES THROUGH THE FILTER CLOTH.
4. FINALLY FILTERATE ENTERS THE DRAINAGE CANAL AND
GOES THROUGH THE OUTLET INTO RECEIVER.
5. AIR IS PASSED TO FLOW IN REVERSE DIRECTION WHICH
FACILITATES REMOVAL OF CAKE
• USES :
1. THE FILTER LEAF IS SATISFACTORY, IF THE SOLID
CONTENT OF THE SLURRY IS NOT TOO HIGH, ABOUT 5%,
i.e., DILUTE SUSPENSIONS.

36. ADVANTAGES
1. IT IS A VERSATILE PEACE OF EQUIPMENT.
IT IS PROBABLY THE SIMPLEST FORM OF
FILTER USED FOR BATCH PROCESS.
2. TO INCREASE THE SURFACE AREA OF
filtration A NUMBER OF UNITS ARE
CONNECTED IN PARALLEL.
3. LABOUR COSTS ARE MODERATE.
4. EFFICINCY OF WASHING IS HIGH.
5. SLURRY CAN BE FILTERED FROM ANY
VESSEL.

37. SWEETLAND FILTER
1. A VARIATONN IS TO ENCLOSE THE FILTER LEAF IN A
SPECIAL VESSEL INTO WHICH THE SLURRY IS PUMPED
UNDER PRESSURE.
2. IN THIS FORM, A NUMBER OF LEAVES ARE CONNECTED TO
A COMMON OUTLET TO PROVIDE A LARGE AREA FOR
filtration.
3. EXAMPLE FOR THIS IS SWEETLAND FILTER
4. IN THIS VESSEL IS CYLINDRICAL AND FILTER LEAVES ARE
ARRANGED SO THAT THEY ARE SUPPORTED BY THE
UPPER PART.
5. LOWER PART CAN BE SWUNG AWAY.
6. THIS PERMITS THE CAKE TO BE DISCHARGED BY
COMPRESSED AIR WHILE REMOVING THE FILTER LEAVES
FROM THE VESSEL.

38. SWEETLAND FILTER

39. META FILTER
• PRINCIPLE :
1. IT FUNCTIONS AS A STRAINER FOR SEPARATION OF PARTICLES.
2. IN THIS METHOD, METAL RINGS CONTAIN SEMICIRCULAR
PROJECTIONS, WHICH ARE ARRANGED AS A NEST TO FORM
CHANNALS ON EDGES.
3. THIS CHANNAL OFFERS RESISTANCE TO FLOW OF SOLIDS. THE
CLEAR LIQUID IS COLLECTED INTO A RECEIVER FROM THE TOP.
• CONSTRUCTION :
1. IT CONSISTS OF A SERIES OF METAL RINGS. THESE ARE
THREADED SO THAT A CHANNAL IS FORMED ON EDGES.
2. IT CONTAINS A GROOVED DRAINAGE COLUMN ON WHICH A
SERIES OF METAL RINGS ARE PACKED. THESE ARE MADE
USUALLY OF STAINLESS STEEL.
3. IT HAVE DIMENSIONS OF ABOUT 15 MM INTERNAL DIAMETER AND
22 MM EXTERNAL DIAMETER.
4. META FILTER IS ALSO KNOWN AS EDGE FILTER.

41. WORKING
1. THESE FILTERS ARE PLACED IN A VESSEL AND MAY BE
OPERATED BY PUMPING THE SLURRY UNDER PRESSURE
OR OCCASIONALLY BY THE APPLICATION OF REDUCED
PRESSURE TO THE OUTLET SIDE.
2. SLURRY PASSES THROUGH THE CHANNALS FORMED ON
EDGES BETWEEN THE RINGS.
3. CLEAR LIQUID RISES UP AND COLLLECTED FROM OUTLET
INTO RECEIVER.
4. IT FUNCTIONS AS STRAINER.
• USES :
1. CLARIFICATION OF SYRUPS.
2. filtration OF INJECTION SOLUTIONS.
3. CLARIFICATION OF INSULIN LIQUORS.
4. filtration OF VISCOUS LIQUIDS.

42. ADVANTAGES
1. IT CAN BE USED UNDER HIGH PRESSURE.
2. RUNNING COSTS ARE LOW.
3. STERILE PRODUCTS CAN BE HANDLED.
4. CHANGE OVER FROM ONE BATCH TO ANOTHER
IS EASY.
5. REMOVAL OF CAKE IS CARRIED OUT
EFFECTIVELY, BY SIMPLY BACKFLUSHING OF
WATER.
6. IT IS EXTREMELY A VERSATILE FILTER.

43. CARTRIDGE FILTER
• PRINCIPLE :
1. IT IS A THIN POROUS MEMBRANE IN WHICH PRE FILTER AND
MEMBRANE FILTER ARE COMBINED INTO A SINGLE UNIT.
2. THE filtration ACTION IS MAINLY SIEVE- LIKE AND THE PARTICLES
ARE RETAINED ON THE SURFACE.
• CONSTRUCTION :
1. IT HAS A CYLINDRICAL CONFIGUARATION MADE WITH
DISPOSABLE OR CHANGEABLE FILTER MEDIA.
2. MADE OF EITHER PLASTIC OR METAL.
3. IT CONSISTS TWO MEMBRANE FILTERS MADE OF
POLYPROPYLENE: A PRE FILTER AND AN ACTUAL FILTER FOR
filtration.
4. A PROTECTIVE LAYER SURROUNDS THEM.
5. CATRIDGES ARE HOUSED IN A HOLDER. HOUSING IS CLOSED
WITH A LID.

45. WORKING
1. SLURRY IS PUMPED INTO THE CARTRIDGE HOLDER.
2. IT PASES THROUGH CARTRIDGE FILTER UNIT BY
MECHANISM OF STRAINING.
3. CLEAR LIQUID PASSES TO THE CENTRE AND MOVES UPTO
COLLECT THROUGH THE OUTLET.
• USES :
1. IT IS IN THE PREPARATION OF PARTICULATE FREE
SOLUTIONSFOR PARENTRAL AND OPHTHALMIC USES.
2. THIS FILTER HOLDER WILL PROCESS 1000 TO 15000 LITRES
OF STERILE SOLUTION PER HOUR.

46. ADVANTAGES
1. STAINLESS STEEL CONSTRUCTION PERMITS
AUTOCLAVING FOR STERILE OPERATIONS.
2. WITH SELF – CLEANING DEVICES ARE ADVANTAGEOUS.
3. THEY ARE NOT BRITTLE, WHEN THEY ARE DRY.
4. RAPID DISASSEMBLING AS WELL AS REUSING OF FILTER
MEDIA IS POSSIBLE.
• DISADVANTAGES :
1. COST OF DISPOSABLE ELEMENTS OFFSETS THE LABOUR
SAVING IN TERMS OF ASSEMBLY AND CLEANING OF
CARTRIDGE CLARIFIER.
2. COMPONENTS ARE NOT QUITE INTERCHANGEABLE.

47. DRUM FILTER
• PRINCIPLE :
1. IT FUNCTIONS ON THE PRINCIPLE OF FILTERING THE SLURRY
THROUGH SIEVE – LIKE MECHANISM ON A ROTATING DRUM
SURFACE, UNDER THE CONDITIONS OF VACUUM.
2. IN ADDITION, COMPRESSION, DRYING, AND REMOVING THE
FILTER CAKE ARE POSSIBLE.
• CONSTRUCTION :
1. IT CONSISTS OF A METAL CYLINDER MOUNTED HORIZONTALLY.
DRUM MAY BE UPTO 3 METERS IN DIAMETER AND 3.5 IN LENGTH
AND GIVES A SURFACE AREA OF 20 METER SQUARE.
2. CURVED SURFACE IS A PERFORATED PLATE, WHICH SUPPORTS
A FILTER CLOTH.
3. DRUM IS RADIALLY PARTITIONED DIVIDING THE ANNULAR SPACE
INTO SEPARATE COMPARTMENTS.
4. EACH OF IT IS CONNECTED WITH AN INTERNAL PIPE.

49. WORKING
1. DRUM ROTATES LESS THAN ONE RPM.
2. AS IT DIPS, VACUUM IS APPLIED IN THIS SEGMENT SO THAT THE SOLID IS
BUILD UP ON THE SURFACE.
3. LIQUID PASSES THROUGH THE FILTER CLOTH INTO AN INTERNAL PIPE AND
VALVE.
4. AS THE DRUM LEAVES THE SLURRY SECTION, IT ENTERS THE DRAINAGE
ZONE.
5. HERE EXCESS OF LIQUID IS DRAWN INSIDE.
6. SPECIAL CAKE COMPRESSION ROLLERS MAY BE INCLUDED IN THIS STAGE.
7. THIS IMPROVES THE EFFICIENCY OF WASHING AND DRYING PROCESS.
• VACUUM IS APPLIED TO CARRY THE SLURRY ALONG WITH THE DRUM.
• DRAINAGE ZONE
• WATER WASHING ARRANGEMENT
• DRYING ZONE – DRY AIR SUPPLY
• CAKE REMOVAL ZONE
1. AS DRUM LEAVES THE DRAINAGE ZONE, IT ENTERS THE WATER WASH
SECTION.

50. WORKING
1. WATER IS SPRAYED ON THE CAKE.
2. WASH LIQUID IS DRAWN THROUGH THE FILTER INTO A
SEPARATE COLLECTING TANK.
3. THEN THE CAKE ENTERS THE DRYING ZONE.
4. IN THIS HOT AIR IS PUMPED INTO IT.
5. FINALLY THE CAKE IS REMOVED USING A DOCTOR KNIFE
AND DISCHARGED.
6. ALL THE THREE STEPS ARE COMPLETED IN ONE
ROTATION OF THE DRUM. NOW THE DRUM IS READY TO
RECEIVE A FRESH LOT OF SLURRY.
• USES :
1. IT IS USED FOR CONTINUOUS OPERATION.
2. FILTER SLURRIES CONTAINING HIGH PROPORTION OF
SOLIDS UPTO 15 TO 30%.
3. USED IN PRODUCTION OF PENCILLIN.

51. ADVANTAGES
1. LABOUR COSTS ARE VERY LOW .
2. IT IS A CONTINUOUS PROCESS.
3. FILTER HAS LARGE SURFACE AREA.
4. SPEED OF ROTATION AND THICKNESS OF THE CAKE CAN
BE VARIED.
• DISADVANTAGES :
1. IT IS AN EXPENSIVE FILTER WITH COMPLEX FUNCTIONING.
2. CAKE TREND TO CRACK DUE TO AIR DRAWN THROUGH BY
THE VACUUM SYSTEM.
3. IT IS SUITABLE ONLY FOR STRAIGHT FORWARD SLURRIES.