Attention should be given to ingress of moisture during fuel handling and storage. Poor quality of fuel leads to poor boiler efficiency.
Combustion of fuel in an oxidizing atmosphere actually occurs when the fuel reaches a particular temperature called flash point for liquid fuels and fire point for solid fuels.
During combustion, a part of the energy released by the fuel is used to convert the moisture contained in the fuel into water vapor. Additionally, the process of combustion also generates water vapor. In most applications the water produced is not used and thus its heat content goes waste.
As the water (moisture) content in the fuel increases, greater part of the energy released by the fuel will be used to convert this moisture to vapor. In case of a boiler this will reduce the net energy that will be transferred to the boiler drum for generating steam.
It is therefore important to give due attention to fuel handling and storage. Often it is seen that solid fuels are stored in the open and get wet in the rain, increasing the moisture content. Also, while purchasing fuels attention should be paid to the quality of fuel procured.
The table below presents the typical enthalpy losses observed across the different boilers: