A spray dryer is something that converts a liquid into a
solid powder. It is used in several areas such as food processing,
pharmaceutical industry, etc. The some spray dried products include instant
coffee, milk powder, paint powder, egg powders, resins and detergents.
To say in simple words, spray drying system is what
undertakes the complete process – right from receiving liquid feed at an end
and packing into a container at the other end from where it is ready to
transport.
However, sometimes, mainly in larger plants, a few other
processes are added as to make the processing cost as much affordable as
possible. Take for example milk processing plant where evaporation technologies
are used to raise the feed solids as much as possible.
What are
the advantages of spray drying?
Most industries where drying is required, use the spray
drying method for its several incredible benefits. In addition to the benefits
for mil processing plants, spray drying also has many benefits for
pharmaceutical industry, such as:
·
Spray-drying is a scalable process for the production
of dry pharmaceutical powders.
·
New devices enable pure drug nanonization and
production of submicron drug carriers.
·
Controlling particle properties during process allows
specific therapy applications.
·
Spray-drying is an effective means to overcome
biopharmaceutical drawbacks of drugs.
·
This technology has become a key player for the
production of inhalable drugs.
How does
spray drying work?
There are different types
of spray drying systems, and spray dryers come in various shapes and sizes
but the way they work remains the same.
Spray drying is an evaporation process –widely used method to
producing powder from liquids.
Basically, spray drying system has three main parts: a large
chamber through which extremely hot air (or a different gas) is passed, a feed
pump to supply raw liquid, and an atomizer that helps the formation of
droplets.
In addition, there is a drum of cyclone which is used to
collect the resulting products.
The solution is fed into spray dryer using a nozzle called
atomizing device – which breaks down the feed solution into individual spheres.
The work of nozzle is to make the droplets as small as possible and maximize
the heat transfer and vaporization rate. The size of droplets varies, depending
on the size of nozzles used.
Drying chambers is like a storage silos. The volume of the
chamber depends on the heath exposure time required for the feed materials
being dried. A burner heats the gas (often air) to force it into the main
chamber where feed solution is atomized to develop into small droplets.
On contact with the hot gas the visible powder particles are
case hardened, but the core is still in molten state. The particles then are made to get into
contact with hot air that strips remaining moisture from the rest of particles.
And thus come out solid particles which are easily made into powder.
