Efficiency: The ratio of the effective or useful output to the total input in any system.

Instrumentation:Instruments for a specific purpose.

Boilerthere are two methods for boiler efficiency

calculation namely:

1.input output method

2.heat loss method

Input-Output Method

The Input-Output efficiency measurementmethod is based on the ratio of the output-

to-input of the boiler. It is calculated by

dividing the boiler output (in BTUs) by theboiler input (in BTUs) and multiplying by 100.

The actual input and output of the boiler aredetermined though instrumentation and thedata is used in calculations that result in the

fuel-to-steam efficiency.

Heat Loss Method

Heat loss method is the method that is used to calculate the percentage amount of heat which is

not useful. This method is very effective used in an attempt to find potential savings of boiler with heat

balance.

There are several factors act as the source of heat loss combustion. These factors will be used to calculate boiler efficiency based on heat loss

method. The source of heat loss can be seen as following below:

a. Heat loss due to dry flue gasHeat loss due to dry flue gas is the heat loss

which is contained in dry flue gas such as CO2, O2 and N2. These gases are one of causes of

heat loss in combustion process. The high temperature of flue gas coming out from boiler

affect amount of heat loss.

The weight and heat loss of dry flue gas of combustion of coal can be calculated as following

formula:Wdfg = mCO2 + mSO2 + mO2 + mN2

Eloss dfg = Wdfg x Cp x (To - Ts)

Where:Wdfg = weight of dry flue gas (kg/kg coal)Eloss dfg = heat loss in dry flue gas (kJ/kg)To = temperature of dry flue gas coming

out from boilerTs = temperature of surrounding air

b. Heat loss due to steam in flue gasThere are two sources of steam contained in flue gas. It is steam from burning H2 and steam from

fuel moisture coupled with steam present in combustion air.

- The calculation formula of heat due to steam from burning H2 is:

WH2O = 9 x H2Eloss H2 = WH2O x (hg - hf)

Where:WH2O = weight of water content (kg/kg coal)

Eloss-H2O = amount of heat loss due to steam from burning process of hydrogen (kJ/kg)

Hg = enthalpy of steam at the temperature of flue gas coming out from boiler

hf = enthalpy of water at surrounding air temperature.

Steam from fuel moisture and combustion airCalculation of heat loss due to steam from fuel

moisture and combustion air: can be seen in the following formula:

Eloss-H2O = (WH2O-coal + WH2O-air) x (Hg - Hf)

Where:Eloss-H2O = amount of heat loss due to steam

from fuel moisture and combustion air

Heat loss due to unburned carbon

The calculation is assumed level of excess air is provided about more 20% and combustion that

occurs only produces unburned carbon about 1% of carbon content in fuel. Calculation of heat loss due to unburned carbon can be seen as following

formula:

Eloss-UC = WUC x HHVcarbon

Where:WUC = weight of unburned carbon (kg/kg)HHVcarbon = highest heating value (kJ/kg)

Eloss-UC = amount of heat loss due to unburned carbon

Heat loss due to radiation

The amount of heat loss due to radiation depends on the rate of heat which is released in

combustion furnace. Based on the ABMA chart (American Boiler Manufacturers Association), at

big heat release rate, the amount of heat loss due to radiation tends to constant. The heat radiation that occurs is estimated 0.2% calorific value of

fuel.

Uncountable heat loss

There are several sources that can cause heat loss in combustion, where the value is too

complicated to be calculated certainly. This heat loss is called as uncountable heat loss. The

amount of uncountable heat loss is about 0.3% of calorific value of fuel.

Eloss total = Eloss-dfg + Eloss-H2 + Eloss-H2O + Eloss-UC + Eradiation + Euncountable