A Major component of the Boiler
Superheater are of Two Type
1. Convective type
2. Radiant type
Convective super heater gives maximum of 80ºC of Superheat while, Radiant Superheat can give 150-300ºC Superheat. Former is more prone to thermal failure & rarely used in ‘flue gas boiler’.
I’ll discuss the convective type super heater.
The basic criterion for the design are
1. Degree of superheat required
2. Steam Dryness available at inlet of super heater
3. Heat duty available.
4. Maximum pressure drop allowed in the system.
5. Flue gas maximum temperature.
6. Type of heat exchanger configuration flow, Cross/Parallel/counter etc.
Flue gas maximum temperature is required to select the MOC of the super heater tubes
for Heat duty following equation shall be validated
M Cp DT = m. (Unit enthalpy of steam)
Where
M = Mass of flue gas
cp = Heat capacity of the flue gas
DT = Temp. drop across super heater
m = mass of Steam
Jana