As spray drying is the most widely used industrial process involving particle
formation and drying, it is natural that the Niro Test Center has the widest
range of test plants available for testing the complete range of spray drying
techniques.
All pumpable products, both heat or non-heat sensitive, can
be processed via Niro’s versatile spray dryers and are able to meet the
requirements for small- or large-scale production. Niro’s spray dryers are
designed to produce precise properties such as particle size, bulk density,
moisture content, solubility, dispersibility etc. to the exact requirements as
defined by the plant operator.
Before selecting the design of a spray
dryer and the type of atomizer, several properties of the source feed and final
product have to be evaluated, hence the need for testing. Factors to be taken
into consideration may include the actual liquid to be dried, particle size,
distribution and powder quality. This might mean testing with more than one
type of technique – thus the opportunities within Niro’s Test Center, where
parallel testing can be arranged, are unmatched.
Overview of spray drying techniques
Co-current Mode: Rotary Atomizer
Atomization is
achieved by feeding liquid onto a high speed wheel. The rotary atomizer is
placed in the ceiling air disperser and operates with a vaned atomizer wheel
for non-abrasive feeds, or with a carbide bushing wheel for abrasive feeds.
Other wheel designs are available for special applications. The particle size
of the powder produced is controlled through change of wheel speed.
Co-current Mode: Two-fluid Nozzle
Atomization is
achieved by using compressed air to atomize the liquid feed. The nozzle is
placed close to the outlet of the ceiling air disperser. This arrangement is
ideal for heat sensitive feeds and has the added advantage of being able to
handle both low and high viscosity liquids. The particle size is controlled by
varying the nozzle flow ratio between compressed air and feed.
Fountain Mode: Two-fluid
Nozzle or Pressure
Nozzle? The nozzle is placed in the conical section of the drying chamber,
spraying upwards into hot air entering the drying chamber through the ceiling
air disperser. The fountain mode has the advantage of spray drying higher solid
feeds and producing coarser powders. Selection of nozzle type depends on the
feed properties and powder specification.