DDPS filter/dryers are batch filtration and drying equipment used in pharmaceutical and chemical applications. They efficiently perform filtration, washing, reslurry, and drying processes. Filter/dryers are available in pilot, semi-works, and production sizes from 0.002 to 16 square meters. Special designs include cGMP, CIP, aseptic, and sterile configurations. The standard filtration and drying process involves filling, filtering, displacement washing, optional reslurry washing, smoothing, drying/cooling, and discharging. Vacuum drying is most common but convection drying is also possible. DDPS offers process engineering support and testing to optimize customers' filtration processes. Filter/dryers provide advantages like enclosure, low maintenance,

1. Filtration and Drying Equipment

2. Typical Scope
 DDPS Filter/Dryers:
– efficiently perform
filtration, washing, reslurry, and drying
– are designed for batch operation
– handle multipurpose pharmaceutical
and fine chemical applications
– are available in pilot, semi-works, and
production units
• Sizes from 0.002m² to 16.0m²

3. Typical Scope
 DDPS Filter/Dryers:
– efficiently perform filtration, washing,
reslurry, and drying
– handle multipurpose pharmaceutical
and fine chemical applications
– are available in pilot, semi-works, and
production units
• Sizes from 0.002 m² to 16.0 m²
Special designs are
available, including:
• cGMP
• CIP
• Aseptic
• Sterile
• Lethal service
• Customization for
other special
requirements

4. Filtration and Drying Process Steps
1. Filling/Charging
2. Filtering
3. Displacement Washing
4. Reslurry Washing
5. Smoothing
6. Drying/Cooling
7. Discharging

5. Filling/Charging
 The first step involves charging the
product to be filtered, typically an
aqueous or solvent based solid/liquid
slurry, into filter from a primary location
(reactor/vessel)
 The filter is usually sized for solids
volume.
― Maximum solids = agitator stroke,
typically 12 - 20 inches.
― Also limited by filtration rate.
.
..

6. Filling/Charging
 The first step involves charging the
product to be filtered, typically an
aqueous or solvent based solid/liquid
slurry, into filter from a primary location
(reactor/vessel)
 The filter is usually sized for solids
volume.
― Maximum solids = agitator
stroke, typically 12 - 20 inches.
― Also limited by filtration rate.
.
..
Filter vessel volume
does not have to
equal reactor volume

7. Filtration Rate
 What controls filtration rate?
― Particle size
― Particle shape
― Cake porosity
― Compressibility
 Typically you cannot measure these factors directly, so testing must be done
to measure their effect:
― Pressure drop
― Filtration rate
― Cake depth
 Tests should be conducted at anticipated cake depth, and more.
 Higher temperature usually = faster filtration.

8. Filtration Constraints
 Minimum cake depth of 3 inches
―Note: This is pertaining to “deep bed filtration”, in which the
filtration mechanism is particle bridging (not absolute
filtration).
 Minimum Filtration Rate
―Typically 4 liter/min-M² (0.1 gpm/ft²)
―Minimum cake buildup rate of 1-inch per hour

9. Filtering
 The second step involves the use of
pressure or vacuum to force liquid
through the solid bed and filter
media. The process is stopped
when solids are visible, or can be
continued until all the liquid is
pushed out.
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..
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..

10. Washing of the Filter Cake:
Displacement
 Here, fresh wash liquid is sprayed
on top of the solid cake. The liquid
is forced through with pressure or
vacuum.
 The purpose of this step is to:
― remove the previous liquid and its
impurities.
― keep cake intact (do not disturb).
― try to close cracks (if cake has any).
― replace previous liquid with fresh
liquid.
.
..

11. Washing of the Filter Cake:
Reslurry
 As an additional washing option,
fresh wash liquid is added and
mixed with the solids. The agitator
is stopped and raised before
filtering.
 The reslurry process is used if:
―extracting or dissolving
impurities
―long contact time is needed
―cake is severely cracked
―displacement wash does not
work
.
..
.
..

12. Washing of the Filter Cake:
Reslurry
 As an additional washing option,
fresh wash liquid is added and
mixed with the solids. The agitator
is stopped and raised before
filtering.
 The reslurry process is used if:
―extracting or dissolving
impurities
―long contact time is needed
―cake is severely cracked
―displacement wash does not
work
.
..
.
..Reslurry is unique to
agitated nutsche filters.

13. Smoothing
 This next step may be used after
any filtration or wash, especially
after the final wash, when gas is
blowing through.
 The agitator will close cracks and
compress the cake to reduce
residual moisture level.
.
..

14. Smoothing
 This next step may be used after
any filtration or wash, especially
after the final wash, when gas is
blowing through.
 The agitator will close cracks and
compress the cake to reduce
residual moisture level.
.
..
The smoothing process
may not be necessary
or useful in some cases.

15. Vacuum Drying
 Vacuum drying requires:
―Heated vessel surfaces (wall, base,
agitator)
―Vacuum source
―Agitation
―Dust filter
.
..
.
..

16. Vacuum Drying
 Vacuum drying requires:
―Heated vessel surfaces (wall, base,
agitator)
―Vacuum source
―Agitation
―Dust filter
.
..
.
..
Vacuum drying is the
most common drying
method in filter/dryers,
and the only method for
dedicated dryers such
as pan and spherical
dryers.

17. Convection Drying
• During the convection drying
phase hot, pressurized gas
(usually nitrogen) can be blown
down through solids and out of
filtrate lines; this will eventually
dry the solids.
• The vessel should be heated.
• Solids may or may not be
agitated.
• Hot gas may or may not be
recirculated.
.
..

18. Convection Drying
• During the convection drying
phase hot, pressurized gas
(usually nitrogen) can be blown
down through solids and out of
filtrate lines; this will eventually
dry the solids.
• The vessel should be heated.
• Solids may or may not be
agitated.
• Hot gas may or may not be
recirculated.
.
..
This method of drying is
applicable to filter/dryers
only, because of their
porous filter plate.

19. Stages of the Drying Process
- Stage One: Removal of free moisture from the wet product.
- Stage Two: Removal of moisture from pores of the wet product.
- Stage Three: Removal of chemically bound moisture.
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1 2 3 4 5 6 7 8 9 10 11 12
Time
%Moisture
0
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DryingRate
Stage One:
Constant Rate
Stage Three:
Diffusion Rate
Stage Two:
Falling Rate
Critical Point
Rate of Drying
Percent Moisture

20. Discharging
 Discharge is accomplished
through the valve/port located on
the vessel sidewall.
 The agitator is used to move
product to the side discharge
valve
―Agitator is slowly lowered until
product is removed.
.
..

21. Discharging
 Discharge is accomplished
through the valve/port located on
the vessel sidewall.
 The agitator is used to move
product to the side discharge
valve
―Agitator is slowly lowered until
product is removed.
.
..The vessel and product
may need to be cooled to
an ambient temperature
prior to discharge.

22. Process Support Capabilities
 Fully supported by in-house process
engineers.
 Filtration testing with 0.002m²
“Pocket” Filter
―Ensures the acceptability of the filter for
the specific customer processes.
 Allows for process
optimization, while limiting product
losses and production down time.

23. Filter/Dryer Advantages
 Totally enclosed and pressure tight (rated to 50 psig/FV at a minimum)
― No operator or environmental contact with the product
― Ideal for high purity, toxic, or flammable materials
 No live load associated with the filter
― Low RPM agitator (8 – 20 rpm typical)
― Lower installation cost
 Low maintenance and operational costs
― No high speed components
― Low motor HP by comparison to other types of equipment (e.g. Centrifuge)
― Agitator only used during drying, smoothing, reslurry washing, and discharge (whereas a
centrifuge motor is always in operation).

24. Filter/Dryer Advantages (cont’d)
 Efficient cake washing
― Extended residence time during displacement washing
― Capable of reslurry washing
― Reduced wash fluid
 Possible increased capacity
― Units typically sized to handle entire batch solids load
 Flexible discharge
― Can discharge dry solids, wet solids, slurries, or liquid
 Drying capability
― Less than 0.1% final product moisture
― Vacuum or blow through drying
― Completely dry material out of the filter

25. Example – Production Unit (1.0m2 units)

26. Example – Production Unit (1.0m2 units)

27.  Additional Resources
– Filtration Webpage
– Filtration Questionnaire
– Contact Us
– Call 908.317.2585 to speak with a DDPS
representative
Thank you