Slag Formation in Boilers

Slag formation occurs when the temperature of the gases exiting the furnace is above the fusion temperature of the fly ash.  At these temperatures, the fly ash melts and gets deposits on the sides of the furnace.

Slag Formation can lead to problems such as
  • reduced heat transfer from the combustion gases inside the furnace to the water
  • It can lead to further overheating of the boiler gases which, in turn, leads to further deposition.
  • Leads to unpredictable behaviour in the boiler
It is necessary to maintain furnace temperature below the fusion temperature of the ash.  The fusion temperature of the ash can be obtained by testing ash samples at laboratories. 
Slagging can also be prevented or minimized by a Slag Screen Arrangement in Boilers.