Fuel heating value is the amount of heat energy that is released by fuel in the oxidation process of chemical elements that exist in fuel. Determination of fuel heating value is important to design combustion furnace of steam boiler. Combustion furnace volume can be determined using following formula:
Vcf = (mf x LHV x ηsb) / hrf
Where:
Vcf = combustion furnace volume (m3)
mf = fuel consumption (kg/s)
LHV = Low Heating Value (kJ/kg)
ηsb = steam boiler efficiency
hrf = heat release rate (kg/m3.s)
From the above formula can be seen that the volume of combustion furnace can be known if the Lower Heating Value (LHV) is known. Fuel heating value can be classified into two types:
- Highest Heating Value
Highest Heating Value (HHV) is the heating value that is obtained from combustion of 1 kg fuel with calculate the heat of steam condensation (water that is produced from combustion in the form of liquid)
- Lowest Heating Value
Lowest Heating Value (LHV) is the heating value that is obtained from combustion of 1 kg fuel without calculate the heat of steam condensation (water that produced from combustion in the form of gas / steam).
Fuel heating value (HHV and LHV) can be obtained in the following ways:
- Taking heating value from existing literature
- Obtaining heating value through testing process in laboratory
Fuel heating value can also be obtained by using equipment in the laboratory; it is oxygen bomb calorimeter as shown in Figure 1. Heating value that is obtained by this equipment can be HHV and LHV. The highest heating value (HHV) can be calculated by following formula:
HHV = (T2 - T1 - TRW) x cv
While lowest heating value (LHV) can be calculated by following formula:
LHV = HHV – 3240 (kJ/kg)
Where:
T1 = temperature of cooling water before it is turned on (oC)
T2 = temperature of cooling water after it is turned on (oC)
TRW = temperature rise of wire igniter = 0.05 (oC)
cv = specific heat of equipment= 73529.6 (kJ/kg oC)
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| Figure 1: Oxygen Bomb Calorimeter |
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