3. About
Fluidized bed dryer (FBD) is well known and widely used equipment
in granulation area of pharmaceutical manufacturing. It is used in
the granulation process for drying the material to get desired
moisture content in the tablet formulation granules required for
perfect compression of tablets.
4. For better understanding, let’s examine each term in the phrase “Fluidized Bed
Dryer.”
Fluidization: It’s the process of making fine solid particles behave like particles
of a fluid, which freely move about, slide past each other, and even collide with
other molecules. Fluidization is done by suspending solid particles in a stream
of fast-moving air
Bed: Refers to the layer of suspended solid molecules
Dryer Equipment: It’s the equipment where wet substances are dried
All contact parts are made out of SS 304/ SS 316 or SS 316L quality material.
5. Components of FBD
For a good understanding of the fluid bed dyer’s working principle, Lets know
its parts. FBD mainly consists of:
I. Machine Tower: Retarding Chamber, product Container, Lower Plenum
II. Inlet Air Handling unit (AHU)
III. Exhaust Air Handling Unit
IV. Ducting: Explosion, Supply and Exhaust
6. Process Chamber/Retarding Chamber
It is cylindrical shell welded with dish end on top of shell which is fabricated
from SS-316 plate. The body flange is welded on bottom side of the shell. It’s
the area just above the product container. The connection between it and the
product chamber is also made air tight with an inflatable gasket.
It’s the place in which fluidization takes place as air is drawn into the main
tower past the bottom bowl and product chamber.
7. Expansion Chamber and Filter Housing Chamber
The expansion chamber forms the middle part of the tower. It’s integrated with the filter
housing chamber that holds the double structure filter bag. Filter bags resemble sacks
suspended over the process chamber.
Air flows upwards during fluidization and may carry in it small particles known as fines. The
filter bags prevent fines from being exhausted.
The filtering bags become clogged with particles and require mechanical shaking to
dislodge this dust layer. For Taking finger bag ups and down, rod less pneumatic cylinder is
given which mounted inside one of the supporting column of FBD. The air outlet is welded
on top dish and an explosion vent nozzle is welded on top dish of the FBD. The respective
ducting pipes are connected with these nozzles.
9. Retarding Chamber Parts
I. Explosion vent
II. Pneumatic Shaking Cylinder on top side; l No.
III. Catching device cylinder
IV. Pneumatic rod less cylinder on chamber support column for lowering the finger bag
V. Duct/opening for Exhaust duct
VI. Finger bag holding assembly
VII. PC stain Finger bag
VIII. SS wire rope for bag holding assembly
IX. Inflatable gasket for sealing finger bag assembly
X. Sight glass for finger bag chamber; l No.
XI. WIP(Wash In Place) nozzle- in bag shaking chamber-l No.
10. Retarding Chamber Parts
XII. Connecting port for Differential pressure across finger bag with differential pressure
transmitter.
XIII. Sight glass -1 No. toughened glass with cover for drying chamber
XIV.Light glass -1 No. toughened glass with cover and lamp on drying chamber
XV. Provision for Dust extraction nozzle with blank (will be connected to clients' central
dust extraction unit)
XVI.Stopper for Product container
XVII.Charging Nozzle with pneumatic actuator
XVIII.Product bowl positioning proxy sensor
XIX. Inflatable gasket at bottom flange for sealing product container from top
11. Product Container With Trolly
This is a conical shaped container having the flange welded at top and at bottom. The wet
product is loaded in the container, as per its working capacity. The product container is
placed in between lower plenum and retarding chamber.
The product container can be transported from one place to another easily with the help of
trolley. This is a tubular structure to support the product container, provided with SS 304
swivel castors and Polyurethane Wheels.
12. Product Container: Accessories
I. Dutch weave mesh
II. “U” beading gasket for sealing mesh
III. Quick change toggle clamp
IV. Sight glass - Toughened glass window with cover
V. Product temperature sensor
VI. Sampling port
13. Base Part (Lower Plenum/Bottom Chamber)
The base part connects to the AHU unit via a stainless steel tube ferrying the clean, hot &
dry air. A butterfly valve along the air inlet tube stops the air intake when closed.
The Lower Plenum is fitted on the bottom side of the machine tower. This plenum is
fabricated from SS-304 plate which has a circular shell welded with bottom flat dish and
flange on top of the shell. The nozzle is provided on plenum for passing inlet air into the
product container. The lower plenum is connected with inlet AHU.
Before production starts, the product chamber and the bottom chamber are interlocked.
An inflatable gasket seal ensures the connection is air tight and leak-proof.
14. Base Part (Lower Plenum/Bottom Chamber)
The lower plenum unit consists of:-
I. Inflatable gasket fitted on flange for sealing bottom side of the product container.
II. Provision Dust extraction nozzle with blank (will be connected to clients' central dust
extraction unit).
III. Drain nozzle with ball valve
15. Inlet Air Handling Unit (AHU)
Air handling unit (AHU) is a rectangular housing which is fabricated from SS 304 sheet inner
skin and pre coated GI outer skin & aluminum frame. The outside portion of the AHU is
filled with PUF insulation and cladded with pre coated GI sheet Both ends are provided
with transition hopper. The supply air pipe is fitted at inlet of AHU which receives air from
the external environment. It consists of filters to provide clean hygienic air from the
atmosphere into the FBD.
17. Inlet Air Handling Unit (AHU): Parts
I. Air filter -Pre filter
II. RTD sensor
III. Face and Bypass Damper
IV. Steam Coil
V. MV filter
VI. HEPA filter
VII. DOP Nozzles- 2 Nos.
VIII.Differential Pressure Gauge for Pre filter & Fine filter
18. Exhaust Air Handling Unit
Handling unit (AHU) is a rectangular housing which is fabricated from SS 304
sheet inner skin and pre coated GI outer skin & aluminum frame. The outside
portion of the AHU is filled with PUF insulation and cladded with pre coated
GI sheet Both ends are provided with transition hopper. The supply air pipe is
fitted at inlet of AHU and blower assembly fitted at other end of AHU.
The Exhaust Air handling unit consists of:-
I. Fine filter
II. Differential pressure gauge
19. Ducting: Explosion Ducting
The Stainless steel bursting disk (Make-BS & B) is fitted in between explosion nozzle and the
ducting. A bursting disk is provided as a safety against any pressure built up or if explosion
takes place in the Retarding Chamber. The bursting disk duct is taken outside the
production area so that it opens to atmosphere without any obstruction.
This entire assembly is fitted on side of retarding chamber as a safety device. It releases the
excess pressure developed inside due to explosion. It also provides the Safety for personnel
working around the equipment
20. Supply Ducting
The ducting in SS304 is provided between FBD lower plenum and the supply air opening of
air handling unit.
It consists of:-
I. Pneumatically actuated ON/OFF Inlet damper valve
II. Inlet Air temperature with relative humidity sensor
21. Exhaust Ducting
This ducting in SS304 for conveying the air through finger bags to the blower suction. Then
the air is exhausted through the blower outlet. The ducting from blower outlet is in client
scope of supply.
A Blower is provided in the system to create an induced draft to pass the heated
conditioned air through wet product and create the fluidization state of material, which
produces a uniformly dry product in a reasonably less time period.
It consists of:-
I. Exhaust temperature sensor IV. Centrifugal Blower
II. Solid Flow sensors V. Motor
III. Pneumatically actuated modulating valve VI. Exhaust Silencer
22.
23. Main Panel
FBD has two panels. Main panel is made of M.S. Powder coated casing and
houses the instrumentation. This panel consists of LV Switchgear, VFD and PLC
with complete power and control wiring. There is pneumatic panel fitted
along with main panel. The main panel is Non flame proof & located in
technical area which behind or top the room.
25. Operating Panel
The machine is Programmable Logic Controller based. The operating panel consists of HMI,
pressure gauge, and FLP control ON/OFF and Emergency button. All are enclosed in SS 304
operating panel which mounted on the machine column. The HMI has printing port to
connect the dot matrix printer LX 310. The printer (LX 310 ) is in client scope. The 250 Nos.
Recipe can be saved in PLC.
28. Automation
To achieve consistency in the product quality it is desirable to minimize/ eliminate the
human elements in monitoring the operational parameters of the machine including the
end point control. It is also desirable to record/ store the critical data which may contribute
to product quality. The operational recipe data can be saved and hard copy(Print Out) can
also be taken out. To incorporate suitable provision in the system of data storage, customer
has to specify parameters which are required to be reproduced. As a standard, following
parameters are recipe based.
29. Automation
I. Product Name
II. Operator Name
III. Batch No.
IV. Batch Date
V. Batch Cycle Timer
VI. Drying Time
VII. Bag Shaking Time
VIII. Cooling Time
IX. Various Faults If any during Cycle.
X. Total air volume
XI. Inlet air Temperature
XII. Exhaust air Temperature
XIII. Product Temperature
XIV. Print interval
30. Technical Specification
Working capacity: 400kg
Material of Construction: Contact Part : SS 316
Non-Contact Part : SS 304/M.S. Cladded with SS sheet
Gasket : Silicon food grade
Damper Valve a) Inlet - 400 mm Dia. Damper valve with Actuator
b) Outlet - 400 mm Dia. Damper valve with actuator proportionate
control
Dust collection nozzle: 40 mm Dia. With blank -2 nos.
(One on Lower Plenum & one on Retardation chamber)
Sampling port : Sampling port is provided on bowl.
WIP nozzle : 1 No -Spray ball is provided above the finger bag
Bag lowering : Rod less Pneumatic cylinder
31. Technical Specification
Bag Shaking : Double acting Pneumatic cylinder
Sieves (Bowl): Dutch weave mesh - MOC- SS 316
Sensors : a) Product temperature sensor on bowl
: b) Inlet air temperature with RH sensor on supply duct
: c) Outlet air temperature Sensor on exhaust duct
: d) Velocity sensor on supply AHU duct
: e) Solid flows sensor on exhaust duct
: f) Air temperature sensor on inlet AHU
Face & Bypass in AHU: Before steam coil with Pneumatic actuated valve for operating the
Face & By pass
32. Technical Specification
Inlet AHU : MOC:- Innerskin-SS-304 pre coated & outer skin-Pre coated GI sheet,
hopper- SS-304
Double Skin AHU-3500 CFM & 1200 mm WC (Supply), Bird mesh, Pre
Filter, Face & Bypass, Steam Coil, Fine Filter, HEPA filter, DP Gauges.
Exhaust AHU : MOC:- lnnerskin-SS-304 pre coated & outer skin-Pre coated GI sheet,
hopper- SS-304 Which consists of pre filter and DP gauge
Pneumatic panel : Pneumatic Panel is Located in technical area, fitted
along with control panel.
33. Technical Specification
Operating panel : The panel is NFLP HMI & FLP control ON/OFF & Emergency Stop
button. All are enclosed in SS Panel. The panel is mounted on machine
column.
Control panel : Non flameproof mounted in the technical area which is behind the
room. All switchgear items are enclosed in M.S. powder coated panel.
Finish : All Internal surfaces have mirror polished and External surface have matt
polished
Power supply : 415 Volt, 50 Hz, 3 Phase
37. Other Components
Other parts include the explosion vent/port that extends from the expansion
chamber. It has a rapture disk tested at a pressure of 2 Bar(as optional item).
Earthing device: Prevents the danger of static electric electricity by absorbing
and grounding the static charges.
39. Things happens just before the drying process starts in Fluidized Bed Drying
AHU preconditioning takes place along with warming up the main tower. Similarly,
compression air inspections should be done to ensure that joints formed by inflation gaskets
are leak proof.
Step 1: Fluidized Bed Dryer: Loading
Loading of materials involves adding a fresh batch of wet granules into the product chamber.
Through negative pressure feeding, materials can be sucked from the high shear mixer
chamber through a feeding tube.
Step 2: Air inlet (Intake)
Switching the blower unit on is done from the control panel. Once the blower is operational,
the air is drawn continuously from the AHU unit and into the tower through the lower
plenum.
40. Step 3: Fluidization
Inlet air is blown up through the static powder bed. As the velocity of the air increases so does
the space between powder particles until the particles become suspended in a bed. The
fluidization process is thought to occur in five stages including smooth fluidization, bubbling
fluidization, turbulent fluidization, and fast fluidization.
Step 4: Drying
The drying process takes place in 3 stages until the endpoint is reached. (At the end-point the
solid particle’s moisture level is equal or less than 1%):
Step 5: Preheating
Wet particles are suspended in the hot and dry air stream. Moisture on the particles’ surface
evaporates as heat flows through the body (conventional heating). The rate of drying slowly
increases as the particles absorb more heat.
The moisture lost during preheating is still small. But the temperature of the bed rises steadily.
41. Constant rate
The rate of drying remains constant as a function of time. In studies, plotting the amount of
moisture lost against time gives a linear graph. In the preheating stage, the bed’s temperature
was rising. But in this stage, the particles remain at the same temperature.
It’s the case because any energy supplied is taken up by the evaporating molecules as they
transition from the liquid to the gaseous state.
Most of the moisture is lost in this stage.
Falling rate stage:
Particles have lost most of their moisture and are nearing the drying end-point. With the
surface moisture reduced, any remaining moisture is drawn from the porous core through
capillary action.
Reduction in evaporation also causes the temperature of the bed to rise. Drying is stopped
when the moisture level falls to less than 1%.
42. Step 6: Filter bags shaking
The blower continuously draws and excels air from the fluidized bed dryer. The airstream may
contain very small particles called fines.
If they make it past the filter bags, they will be expelled into the surroundings. The filter bags
capture the fines in their pores. But this causes the formation of a dust layer that clogs the
filter bags causing a pressure drop.
Mechanical shaking is the best way to remove the dust layer, and it’s done by the pneumatic
cylinders at the set intervals.
And since we have two filtering chambers, the shaking is alternated between the two.
Step 7: Exhausting & Secondary filtering unit (Optional)
Air exhausted from the fluidized bed dryer may go through a second filtering stage. This
might help remove any particles that made it past the filter bag system.
43. Step 8: Discharging of dried material
Discharging refers to the removal of dried materials from the fluidized bed dryer. It can be
done manually by unlocking and wheeling the product container on its trolley to the next
process equipment.
Alternatively, vacuum conveying can be carried out by connecting the product container with
a tube and creating negative pressure for suction using a vacuum transfer system.
After drying, the next process is milling carried out in the conical mill or conmill.
44. Brief Process Description
I. Fix up the clean finger to the holding ring.
II. Lift up the finger bag and inflate the gasket.(Manual Mode)
III. Place the filled product bowl inside the dryer
IV. Inflate top and bottom gaskets of the dryer body and Bottom pan
V. Set the timer for required drying time & cooling time.
VI. Set the temperature of heater
a) Start the machine.
b) Blower will start.
c) Heater will on.
VII. Open the inlet & Exhaust dampers
45. Brief Process Description
VIII. After drying is over, the machine will be switched over to cooling time. (Heater will off)
IX. Blower off.
X. Close the damper valve.
XI. Deflate the top and bottom gaskets of dryer body and Bottom pan.
XII. Remove the bowl.
XIII. Take the dry product for next process.
Note:-The perfect process is to be validated by client
46. Important Parameters of Drying Process
The rate of drying depends on several factors including the product’s characteristics,
process parameters, and even the design of a fluid bed dryer (fluidized bed dryer). For
instance:
Position of the air distribution plate:
It has a direct bearing on the airflow pattern inside the fluid bed dryer.
The body’s shape:
The shape of the tower has also been shown to impact the drying rate with an annular
shape preferred.
47. The temperature of the inlet air:
Increasing the inlet air temperature also increases the rate of heat and mass transfer. Both of
which increase the rate of drying. But it’s not always possible to use high operating
temperatures, especially for heat-sensitive materials. For instance, when drying Ibuprofen
the temperature must not exceed 60oC. In a study, where the researchers increased the
operating temperature from 60 to 80oC, there was a small increase in the drying rate. Though
this was offset by the reduction in the energy efficiency of the fluidized bed dryer. So it’s
always better to use the optimum operating temperature even if the drying time may be
slightly prolonged.
48. The humidity of the air:
The air must have minimum moisture levels for faster drying. We recommend the desiccant
wheel for maximum dehumidification.
The flow rate of air (Air Flux):
The right rate of airflow should be neither too fast nor slow. It should be at an optimum rate.
Still increasing the air velocity may promote more mass and heat transfer. It may also improve
the energy-efficient ratio, and reduce the drying time leading to less energy consumption.
49. Product Parameters
In product parameters, two things are considered:
I. The products moisture content
II. Amount of product loaded
For instance, if the initial moisture content is 30%, more time will be required
compared to a material with a moisture content of only 10%.
Larger batch quantities will also need more time in the fluidized bed dryer than smaller
batch quantities.
50. Safety Features
I. Positive earthing with low voltage relay.
II. A bursting disc is provided as a safety against any pressure build up in main shell.
III. Interlocks of inflatable gaskets (pressure switch is provided
IV. Overload relays, MCB's, Emergency stop are provided in electric circuit.
V. Solid flow monitor sensor provided against finger bag rupture.
VI. Proxy switch is provided to sense the bowl in position & interlock with machine.
51. FAT Procedure
Factory Acceptance Test procedure shall be as follows:
After the computation of erection work of the machine, client shall be informed to
perform the Factory Acceptance Test [FAT].
Client shall perform the FAT at the manufacturer site and record all the data in the
prescribed FAT document as per the details given below:
I. Test criteria
II. Design Verification Checklist
III. Deficiency and Corrective Action Report
IV. Pre-Installation requirements
V. Final report
52. Advantage of FBD
I. Fluidized bed dryer (fluidized bed dryer) achieves faster drying rates with the drying
time ranging from 20 minutes to 40 minutes.
II. With the material in a fluidized state, there are no hot spots.
III. It enhances the product’s properties i.e. its porosity.
IV. fluidized bed dryer dryers don’t have lots of moving parts and require little
maintenance.
V. It offers high containment of material, and still offers viewing and sampling ports
allowing the operator to monitor the process easily. Sensors also provide constant
feedback on process parameters such as the product temperature, outlet air
temperature, and inlet air temp, allowing the PLC control to make any adjustments
as required.
53. Advantage of FBD
VI. It’s suited for thermosensitive products because you can operate it at relatively low
temperatures. For instance, the air is usually at 60o The product doesn’t come into
contact with hot surfaces minimizing the likelihood of the powder material getting
burned.
VII. With PLC control and using touch screen inputs for programming the process
parameters, the fluidized bed dryer is easy to use, less labor-intensive, and gives
consistent results.
VIII. The drying is uniform. And by using the AHU, it’s easy to regulate the temperature of
the air stream.
54. Disadvantages of FBD
I. Electrostatic charges tend to develop on the particles, which will impair fluidization.
But upcoming FBD machines overcome this problem through sufficient earthing.
II. Sometimes the materials might shrink on contact exposure to high temperatures,
but with our capable control system, it is simple to maintain the perfect fluidizing
conditions.
III. The vessel gets subject to lots of pressure, which might increase the risk of
accidents. Though, we offer explosion-proof designs of 10 bar or 12 bar.
IV. In the fluidized state, particles are constantly colliding with each other leading to
attrition. Considerable particle size reduction will result in very fine powders..
