nozzle dryers

15
Presented to- Mrs. Neha Singh Presented by- Ridham Walia Roll No.- 14/PFT/003 NOZZLE DRYERS

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Page 1: Nozzle dryers

Presented to- Mrs. Neha SinghPresented by- Ridham Walia

Roll No.- 14/PFT/003

NOZZLE DRYERS

Page 2: Nozzle dryers

CONTENTS

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

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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.

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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.

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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

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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.

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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

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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.

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Pneumatic nozzles

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*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

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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.

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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

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THANK YOU