BUCHI Nano Spray Dryer B-90 - Manual (Page 25)

4 Description of function
25 B-90 Operation Manual, Version B
4 Description of function
This chapter explains the basic working principle of the Nano Spray Dryer B-90 Basic (‘open loop’
only) and the Nano Spray Dryer B-90 Advanced (equipped with O
2
-sensor and inert gas regula-
tion valves for ‘closed loop’ mode). It also shows how the instruments are structured and provides a
general functional description of their assemblies.
4.1 Functional principle
The Nano Spray Dryer B-90 models have been designed to produce particles out of a solution or
suspension with a particle size between 0,3 µm–5 µm by drying or encapsulation at a yield rate of up
to 90 %. The output particle size depends mainly upon the chosen spray cap. The Nano Spray Dryer
B-90 also allows processing of nano particles (<100 nm) in nanosuspensions or emulsions e.g. for
encapsulation. The drying gas flow and the product stream are described below.
4.1.1 Drying gas circuit
The sprayed liquid is accompanied by a co-current gas flow. For highest yields, a controlled gas
flow at a sufficient quality and a defined temperature is required. To ensure this, a flow regulator and
heating loop has been implemented
a The drying and transport gas enters the instrument
via the “Drying gas inlet”.
b The gas flow is monitored by a “Flow meter”
which influences the “Gas regulator”.
c Subsequently the “Electrical heater” heats up the
gas to the desired drying temperature.
d Via the “Inlet temperatur sensor” the heater is
regulated to achieve the desired gas temperature.
e The “Relative pressure sensor” compares the in-
ternal to the environmental pressure. In the event
of a massive pressure loss (e.g. a leakage) this
sensor stops the drying process.
f In ‘closed loop’ mode, as part of the safety loop
the “Oxygen sensor” supervises the percentage of
oxygen in the drying gas. In emergency, it stops
the process.
g The “Outlet temperature sensor” is located after
the particle collector. The temperature drop
between inlet and outlet temperature sensor is
measured as a process value.
h The “Outlet filter” is a safety relevant item. It re-
tains possibly harmful particles towards the envi-
ronment in ‘open loop’. In ‘closed loop’ the outlet
filter is an essential part for cleaning the recycled
gas from unwanted residues and impurities.
i The “Drying gas outlet” works as an exhaust.
a
Drying gas inlet
b
Flow meter
c
Electrical heater
d
Inlet temp. sensor
Drying cylinder
Electrical particle
collector
e
Rel. pressure sensor
g
Outlet temp. sensor
h
Outlet filter
i
Drying gas outlet
Oxygen sensor
Gas regulator Feed pump
Spray head
f
safety loop