QUANTITY OF AIR REQUIRED FOR BURNING OF COAL
ER. PARTHAPRATIM BHATTACHARYYA
![ER. PARTHAPRATIM BHATTACHARYYA]()
ER. PARTHAPRATIM BHATTACHARYYA
MANUFACTURING ADVISOR at Parcon India Private limited
Stoichiometric or Theoretical quantity of air required to completely burn 1kg of coal is 7kg which has been detailed below. Since our system is not full proof and the heaters / boilers work at around 60% - 65% efficiency level, hence some excess air is required for complete combustion of coal. This is around 50% of theoretical value mentioned above which makes it 10kg air required per kg of coal. Excess air is used as per requirement for proper burning of coal.Anything above this will cause heat loss.
Theoretical Air Quantity (Stoichiometric Quantity) is calculated based on the chemical reaction between the elements of coal namely carbon , hydrogen , sulphur and oxygen present in coal.
Carbon combines with oxygen to form carbon dioxide and heat.
C+ O2 = CO2
12 C + 32 O2 = 44 CO2
1 C + (32/12) O2 = (44/12) CO2
1 g Carbon + 2.67 g Oxygen = 3.67 g Carbon Dioxide
Hydrogen combines with oxygen to form water and heat
2 H2+ O2 = 2H2O
4 H2 +32 O2 = 36 H2O
H2 ?+ (32/4) O2 = (36/4) H2O
1 g Hydrogen +8 g Oxygen = 9 g Water
Sulphur combines with oxygen to form sulphur dioxide
S + O2 = SO2
32 S + 32 O2 = 64 SO2
1 S + (32 /32 ) O2 = (64 /32) SO2
1 g Sulphur +1 g Oxygen = 2 g Sulphur Dioxide.
The coal we use normally has 57.2 % Carbon, 2.2 % Hydrogen, 0.5 % Sulphur and 6.9 % Oxygen.
The theoretical oxygen required to burn this coal is then
2.67 x C % + 8 x H% + 1 x S % - O% = 1.64 g of Oxygen for 1 g of Coal.
Air contains 23.2% by weight of oxygen.
The theoretical air required to burn the 1g coal is
= 1.64 / 23.2% = 7.1 g of Air for 1 g of Coal or 7.1kg air per kg of coal.
This is the theoretical air required to burn 1gm of coal.
Now considering 50% excess air requirement, this value becomes 10.65kg of air per kg of coal for complete combustion.