SPRAY DRYER !!!

Hey guys , lets throw some light into the concept of Drying today !!!

Generally speaking , Drying refers to the removal of minute amount of water vapour from the feed . There are many types of Drying , the most prominent of them being Rotary Drying , Tunnel Drying , Spray Drying , etc .

In all of these basic UNIT OPERATIONS , Spray Drying holds a numero uno status from quite some time . What’s so special in this process that it survived the turmoil of humanity right from the 1870s , when new process come and then sink without a trace  ??? Lets know then !!!

First of all …..WHY SPRAY DRYING WHEN WE CAN JUST EVAPORATE ???   no great energy wastage from our side too …then why ??

The answer’s SIMPLE  ---- In the world there are a galore of thermally sensitive and thermally resistant  materials . We simply cannot dry them in the open sun …The former might just evaporate without a trace while the latter stubbornly sits there all day no matter you dry it for weeks on a trot !!! Tadaa !! Hence , Spray Drying

Lucidly speaking , Spray Drying involves the production of a dry , granular , free-flowing powder from a liquid or a slurry by the rapid cooling with hot gases .

It is a CONTINUOUS , PARTICLE PROCESSING , MASS-TRANSFER operation !!!

In the process of Spray Drying , the liquid stream or feed  , as we chemmies call it , is first atomized using a suitable Atomizer and is then sprayed at a high speed over hot gases present in the apparatus . The hot gas normally is Air , but if the feed is oxygen reacting we use Nitrogen . Next the hot gases dry up the stream , which is then taken into a Cyclone for separation of the particles produced . In addition , a bag filter can also be used to get finer particles .

Spray Drying mainly involves four stages :-

a) Concentration of the feed

b) Atomization of the slurry

c) Droplet drying

d) Separation using cyclones

 

Don’t get confused with the stages , but Spray Drying is a SINGLE-STEP process . The above stages occur at blinding velocity that they all are considered one continuous entity .

ADVANTAGES :

1) It is continuous.

2) Can be made Fully – Automated easily

3) It can be used irrespective of the feed capacity .

4) We can produce nearly-perfect spherical particles .

5) The weight and volume of feed can be reduced . As a matter of fact , Spray Drying reached it’s full glory during WW2 , where the need to reduce the weight of food for the army was enormous .

 

USES :

Used in the FOOD industry extensively , especially in the Dairy Industry .

The Pharmaceutical Industry found a great way to make powders for tablets .

In recent times the Ceramic field is catching up with this concept too !!!

 

DISADVANTAGES :

1) Very energy extensive

2)  High operating cost

3) Ineffective in producing a constant granular size of particles

Hence , the concept of NANO SPRAY DRYERS is the talk of the town nowadays .We will discuss about it sometime later in the future for sure !!!

Well , for the never ending practical thirst for the geek community of the world , here’s a special gift just for you

check out

http://www.gbm.dk/gbm/SD-e.htm for the working model of a common spray dryer !!!

au revoir guys !!!