Nozzle dryers...

Presented to- Mrs. Neha SinghPresented by- Ridham Walia

Roll No.- 14/PFT/003

NOZZLE DRYERS

CONTENTS

* Spray Drying* Types of atomizers: Rotary atomizer* Pressure Nozzle atomizer* Two- fluid nozzle atomizer* Pneumatic nozzle* Common usesReferences

Spray Drying

Definition-

A special process which is used to transform the feed from a liquid state into a dried particulate form (Powder or Particles) by spraying the feed into a hot drying medium.

Contd.*Atomizer or spray nozzles are used to disperse the liquid or

slurry into a controlled drop size spray. *Most common of these are rotary disks and single-fluid high

pressure swirl nozzles. *Atomizer wheels are known to provide broader particle size

distribution.*Alternatively, for some applications two-fluid or ultrasonic

nozzles are used. *Depending on the process needs, drop sizes from 10 to 500 µm

can be achieved with the appropriate choices. *Most common applications are in the 100 to 200 µm diameter

range. The dry powder is often free-flowing. *For many industries a standard pressure nozzle operating in the

3,000-4,000 psi and 175-400°F will excel.

Types of atomizers: Rotary atomizer

*Advantages:•Handles  large  feed  rates  with  single wheel or disk•Suited  for  abrasive  feeds  with  proper design•Has negligible clogging tendency•Change of wheel rotary speed to control the particle  size distribution•More flexible capacity 

*Limitations :•Higher energy consumption compared to pressure  nozzles•More expensive•Broad spray pattern requires large drying chamber  diameter

Pressure nozzle atomiser

*Liquid is forced at a high pressure (700-2000 kPa) through a small orifice. Nozzles have a maximum flow rate of 1 L/h.

*Typical pressures range from 300 to 4000 psi. *Dryers with pressure nozzles typically contain drying chambers that are narrow in diameter and tall in height.

* The small orifice facilitates clogging, so pressure nozzles are seldom used when the feed is highly concentrated.

*Grooves on the inside of the nozzle cause the spray to form into a cone shape and then reform to use the full volume of the drying chamber.

Pressure Nozzle*Advantages:* Simple, compact and cheap* No moving parts* Low energy consumption

*Limitations:* Low capacity (feed rate for single nozzle)* High tendency to clog* Erosion can change spray characteristics

Two - fluid nozzle atomiser

*Compressed air creates turbulence, which atomises the liquid.

*The operating pressure is lower than the pressure nozzle, but a wider range of droplet sizes is produced.

*Both types of nozzle atomiser are susceptible to blockage by particulate foods, and abrasive foods gradually widen the apertures and increase the average droplet size.

Pneumatic nozzles

*Advantages:* Simple, compact and cheap* No moving parts* Handle the feedstocks with high‐viscosity * Produce products with very small size particle

*Limitations:* High energy consumption* Low capacity (feed rate)* High tendency to clog

Pneumatic nozzle

Common Uses / Installations of Spray Drying Nozzles

Dairy Industry: drying full cream and skim milk, cheese, whey, and baby formula.

Foodstuffs: instant coffee, edible plant proteins, tomato, egg, baking products, yeasts, and other extracts.

Chemical industry: polycarbonate and polyvinyl products among many other organic and inorganic chemicals. Ceramics, soaps and detergents, agricultural products, dyestuffs, mineral and ore products, and cellulose.

REFERENCES

en.wikipedia.org ppt on spray drying of foods PDF file on Classification of dryers Spray drying technology: An overview Indian Journal of Science and Technology

THANK YOU