Buchi Nano B-90, Руководство по эксплуатации

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4 Description of function
27
B-90 Operation Manual, Version B
Processing inside the drying cylinder
The following draft offers a more detailed view about the basic spray drying process. The drying
gas (
a
) passes the heater (
b
) and the vertically or angular aligned spray head (
e
). The injected
micro doplets of the sample material are dried while beeing vortexed in the gas flow inside the spray
cylinder (
f
). An electric field is generated by high voltage between the collecting electrode (
h
) and
the HV-electrode (
i
). While the HV-electrode deflects the particulate material, the collecting electrode
attracts them. Thus, particles are depositing at the inside of the collecting electrode (
g
).
















a
b
c
d
e
f
g
h
i
j
k
l
a
Drying gas inlet (optional with inlet filter and Aspira-
tor)
b
Electrical heater
c
Inlet temperature sensor
d
Display/Control
e
Spray head (angular or vertical installation)
f
Spray cylinder and drying section
g
Finished product at particle collecting electrode
h
Particle collecting electrode
i
HV–electrode
j
Outlet temperature sensor
k
Outlet filter
l
Drying gas outlet (in ‘closed loop’ connected to Inert
Loop B-295 and Aspirator)
4.2 Spray generation
The Nano Spray Dryer B-90 uses piezotechnology to generate precisely controlled micro droplets
from bulk liquids without the use of propellants.
push
push
pull pull
The spray head includes a piezoelectric actuator with
a thin stainless steel membrane. The membrane has
an array of micron-sized holes (spray meshes of 4.0,
5.5 or 7.0 µm hole size) and vibrates at ultrasonic
frequency (60 kHz). Because of these vibrations
the membrane eject precisely sized droplets at high
speed.
NOTE
The smaller the mesh size, the smaller the ejected droplets and dried particles. Since the vibrations
frequency is fixed, a smaller mesh size will have less throughput per time.
4.3 Heating system
The compact heater module provides optimal energy input to heat the drying gas up to 120 °C. The
heating system consists of an electrically heated porous metal foam to minimize the heat–up time and
to generate a laminar gas flow towards the drying section. The heating control is based on a plug-
gable PT–1000 temperature sensor.