Drying | Drying Systems Used in Sizing | Cylinder Drying / Hot Air Drying / Infrared Drying / Combined Drying

Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. In sizing, drying is necessary to bring the sized material hard.

1. Cylinder Drying: In this type of m/c, drying is done by passing over hot cylinders.

a) Two Cylinder Drying:
  1. In this drying process, two copper cylinder are used in which one cylinder is large diameter & other is small comparatively.  
  2. Firstly warp sheet is passed below the small cylinder & then over the bigger one.  
  3. The yarn is dried while traveling through the circumstances of the cylinder.

Two Cylinder Drying
Advantages:
1. Simple process & cheap.
2. Less risky.
3. Temp. uniform.
4. Almost uniform drying.

Disadvantages:
1. Slow process.
2. Drying efficiency is low.
3. Irregular drying.
4. Due to sticky property of cylinder uneven drying.

(b) Multi Cylinder Drying:
  1. In this type of m/c, the drying unit consists of 5 to 7 or 11 cylinders having same diameter are used.
  2. All cylinders may be steel cylinders or first two cylinders are teflon coated & rest of aresteel cylinder.
  3. The cylinders are heated by passing steam.
  4. Heat in initial cylinder is low & gradually increases when moved towards finalcylinder.
  5. If large amount of heat is given to the initial, the sized may be backed.
  6. If finer yarn is used, then no need to use excess cylinder.
Multi Cylinder Drying
Advantages:
1. High speed process.
2. Uniform drying.
3. Non- sticky so smooth drying.
4. Drying efficiency high.
5. Less time required.

Disadvantages:
1. For high viscosity, stick properly may observed.
2. For friction, yarn hairiness.
3. Shinning effect.
4. Yarn shape may hamper.
5. Possibility of yarn flaten.

2. Hot Air Drying:
  • In this m/c, the drying unit is a closed chamber containing a number of guide rollersthrough warp yarn.
  • Hot air blown into the chamber causing the moisture in the yarn toevaporate.
  • Exhaustion should be used to throw away the moisture.
  • If moisture remains inside the chamber it may condense & again fallon the yarn.
  • Hot air should be continuously passed through the chamber, so theprocess becomes somewhat costly.
Hot Air Drying
Advantages:
1. Regular drying.
2. Not shinning effect.
3. Non-sticky property.
4. High speed drying.

Disadvantages:
1. Costly process.
2. For closed chamber, reqd more time.
3. Less suitable for fine yarn.
4. Difficult to maintain temperature.

3. Infrared Drying:
  • In this machine, the heating chamber consists of a plate which is constantly heated by gas flame.
  • The warp sheet is passed over the plate & dried in the process.
  • When gas flames are not used, then electronic plate may be used.
  • Arrangement should be made to through out the moisture removed from the yarn. This m/c is not used signally.
Advantages:
1. No shining effect.
2. Drying efficiency high.

Disadvantages:
1. Yarn may burn.
2. Higher cost.
3. Difficult to maintain uniform heating.
4. Risk of accident.
  4. Combined Drying:
  • In this type of m/c, preheating is done as cylinder drying method.
  • And final drying is done by hot air drying method or infrared drying method.
Infrared Drying
Advantages:
1. Regular drying.
2. Drying efficiency high.
3. Speedy process.

Disadvantages:
1. Shinning effect.
2. High cost. 

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