The combustion efficiency of a boiler is the indication of burner’s ability to burn fuel. The two parameters which determine the burner efficiency are unburnt fuel quantities in exhaust and excess oxygen levels in the exhaust. As the amount of excess air is increased, the quantity of unburnt fuel in the exhaust decreases.

Boiler efficiency may be indicated by Combustion Efficiency - indicates a burners ability to burn fuel measured by unburned fuel and excess air in the exhaust Thermal Efficiency - indicates the heat exchangers effectiveness to transfer heat from the combustion process to the water or steam in the boiler, exclusive radiation and convection losses

· PDF fileFrom the table, the boiler combustion efficiency is 78.2% (E1). Tuning the boiler reduces the excess air to 9.5% with a flue gas minus combustion air temperature of 300°F. The boiler combustion efficiency increases to 83.1% (E2).

Boiler Efficiency and Combustion A broad overview of the combustion process, including burner types and controls, and heat output and losses. This Module is intended to give a very broad overview of the combustion process, which is an essential component of overall boiler efficiency.

Additionally, under normal operating conditions, water/steam injection can result in a 3-10% boiler efficiency loss. Many times water or steam injection is used in conjunction with other NOx control methods such as burner modifications or flue gas recirculation.

The combustion efficiency of a boiler signifies the burner’s capacity to burn fuel. It has two parameters that determine the burner efficiency: unburnt fuel supplies in the exhaust and excess oxygen levels in the exhaust. As the value of excess air is increased, the amount of unburnt fuel in the exhaust decreases.

· PDF fileThermal efficiency of boiler is defined as the percentage of heat input that is effectively utilised to generate steam. There are two methods of assessing boiler efficiency. 1)The Direct Method:Where the energy gain of the working fluid (water and steam) is compared with the energy content of the boiler fuel.

· PDF filePerformance of the boiler, like efficiency and evaporation ratio reduces with time, due to poor combustion, heat transfer fouling and poor operation and maintenance. Deterioration of fuel quality and water quality also leads to poor performance of boiler.

Carbon dioxide - CO2 - is a combustion product and the content of CO2 in a flue gas is an important indication of the combustion efficiency. Optimal content of carbon dioxide - CO2 - after combustion is approximately 10% for natural gas and approximately 13% for lighter oils.

The temperature of the combustion air entering the boiler is called ambient temperature, which can have a relatively noticeable effect on boiler efficiency. A variation of 40 degrees Farenheit can affect boiler efficiency by 1% or more, so this can drastically affect your operations.