Answer - Then Biggest Loss in the Boiler is dry flue gas.
Most of the fuel is burned during the combustion process, however, some fuel particles are left unburned and are deposited with the ash. The amount of unburned fuel increases when the size of fuel particles delivered to the furnace is big, as this reduces the surface area of air and fuel particles in contact.
This takes into consideration any fuel that would have been lost that would have otherwise been burned to produce heat. All heat losses from dry flue gas are severe. Most of the heat is lost if the flue gases leaving the boiler are at a higher temperature than the temperature at which it is designed, which results in decreased boiler efficiency.
Then Biggest Loss in the Boiler is
Then biggest loss in the boiler is dry flue gas. If the flue gases leaving the boiler are hotter than the temperature at which it was designed to operate, the majority of the heat is wasted, which lowers boiler efficiency.