understanding the nutsche filtration and drying process
TRANSCRIPT
Filtration and Drying Equipment
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
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
Filtration and Drying Process Steps
1. Filling/Charging2. Filtering3. Displacement Washing 4. Reslurry Washing5. Smoothing6. Drying/Cooling7. Discharging
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.
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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.
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Filter vessel volume does not have to equal reactor volume
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.
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
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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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.
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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
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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
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..Reslurry is unique to agitated nutsche filters.
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.
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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.
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The smoothing process may not be necessary or useful in some cases.
Vacuum Drying Vacuum drying requires:
―Heated vessel surfaces (wall, base, agitator)
―Vacuum source―Agitation―Dust filter
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Vacuum Drying Vacuum drying requires:
―Heated vessel surfaces (wall, base, agitator)
―Vacuum source―Agitation―Dust filter
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Vacuum drying is the most common drying method in filter/dryers, and the only method for dedicated dryers such as pan and spherical dryers.
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.
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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.
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This method of drying is applicable to filter/dryers only, because of their porous filter plate.
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
% M
oist
ure
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Dry
ing
Rat
e
Stage One:Constant Rate
Stage Three:Diffusion Rate
Stage Two:Falling Rate
Critical Point
Rate of DryingPercent Moisture
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.
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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.
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.
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).
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
Example – Production Unit (1.0m2 units)
Example – Production Unit (1.0m2 units)
Additional Resources– Filtration Webpage– Filtration Questionnaire– Contact Us– Call 908.317.2585 to speak with a DDPS
representative
Thank you