One thing we must remember while designing super heater.. Better the steam dryness compact will be the super heater.
One must always ensure that dry steam (99%) is coming in the superheater.
Just to give you the picture..
- for 98% Dry steam.. the unit energy required to make steam 100% dry+70ºC superheat
is : 61.5kcal/kg
- for 99% Dry steam.. the unit energy required to make steam 100% dry +70ºC superheat
is : 56.1kcal/kg
i.e if you give 99% dry.. 61.5-56.1 = 5.4Kcal/kg i.e for 6000kg/hr its 40KW less energy is required.
Lower heat demand.. means lower heat transfer area.
Now Dryness can be improved by giving dimister pad or giving external equipment to improve steam dryness.