# Fuel and Combustion Formulas

Fuel and Combustion | ||||||||

S. | Description | Symbol | Formula | Example | ||||

No. | ||||||||

1 | Gross calorific value | GCV | 80.8 * C + 22.45 * S + 339.53 * H – 35.89 * O | C | 70.86 | |||

kcal/kg-fuel | S | 0.58 | ||||||

C | Carbon content in fuel, wt% | H | 3.87 | |||||

S | Sulphur content in fuel, wt% | O | 6.08 | |||||

H | Hydrogen content in fuel, wt% | GCV | 6834 | |||||

N | Nitrogen content in fuel, wt% | Target | – | |||||

2 | Net calorific value | NCV | GCV – 52.53 * H – 6 * m | GCV | 6007 | |||

kcal/kg-fuel | H | 3.2 | ||||||

GCV | Gross calorific value of fuel, kcal/kg-fuel | m | 1.3 | |||||

H | Hydrogen content in fuel, wt% | NCV | 5831 | |||||

m | Moisture content in fuel, wt% | Target | – | |||||

3 | Useful heat value | UHV | 8900 – 138 * ( Ash + m ) | Ash | 14.99 | |||

kcal/kg-fuel | Ash | Ash content in fuel, wt% | m | 1.93 | ||||

m | Moisture content in fuel, wt% | UHV | 6565 | |||||

Target | – | |||||||

4 | Standard coal factor | SCF | ( 1 – m / 100 ) * NCV / 7000 | m | 1.93 | |||

– | m | Moisture content in fuel, wt% | NCV | 6500 | ||||

NCV | Net calorific value of fuel, kcal/kg-fuel | SCF | 0.911 | |||||

Target | – | |||||||

5 | Stoichiometric Combustion | SCA | Formula-1 | NCV | 6500 | |||

Air | kg/s | NCV * F | F | 11000 | ||||

or | 709 * 3600 | SCA | 28.01 | |||||

Minimum Combustion | NCV | Net calorific value of fuel, kcal/kg-fuel | Target | – | ||||

Air | F | Fuel rate in kiln, kg/hr | ||||||

Formula-2 | C | 70.78 | ||||||

[ 0.11594 * C + 0.34783 * ( H – O / 8 ) + 0.04348 * S ] * F | H | 3.46 | ||||||

3600 | O | 5.12 | ||||||

C | Weight% of Carbon in fuel | S | 0.71 | |||||

H | Weight% of Hydrogen in fuel | F | 11000 | |||||

O | Weight% of Oxygen in fuel | SCA | 28.17 | |||||

S | Weight% of Sulphur in fuel | Target | – | |||||

F | Fuel rate in kiln, kg/hr | |||||||

Formula-3 | m | 1.9 | ||||||

10.478 * ( 100 – m ) * GCV * F | GCV | 6700 | ||||||

100 * 7000 * 3600 | F | 10500 | ||||||

m | Weight% of Moisture in fuel | SCA | 28.70 | |||||

GCV | Gross calorific value of fuel, kcal/kg-fuel | Target | – | |||||

F | Fuel rate in kiln, kg/hr | |||||||

6 | Specific Stoichiometric | SSCA | Formula-1 | NCV | 6500 | |||

Combustion Air | kg/kg-fuel | NCV | SSCA | 9.17 | ||||

or | 709 | Target | – | |||||

Specific Minimum | NCV | Net calorific value of fuel, kcal/kg-fuel | ||||||

Combustion Air | ||||||||

Formula-2 | C | 70.78 | ||||||

0.11594 * C + 0.34783 * ( H – O / 8 ) + 0.04348 * S | H | 3.46 | ||||||

C | Weight% of Carbon in fuel | O | 5.12 | |||||

H | Weight% of Hydrogen in fuel | S | 0.71 | |||||

O | Weight% of Oxygen in fuel | SSCA | 9.22 | |||||

S | Weight% of Sulphur in fuel | Target | – | |||||

Formula-3 | m | 1.9 | ||||||

10.478 * ( 100 – m ) * GCV | GCV | 6700 | ||||||

100 * 7000 | SSCA | 9.84 | ||||||

m | Weight% of Moisture in fuel | Target | – | |||||

GCV | Gross calorific value of fuel, kcal/kg-fuel | |||||||

Formula-4 | SCF | 0.925 | ||||||

10.478 * SCF | SSCA | 9.69 | ||||||

SCF | Standard coal factor, – | Target | – | |||||

7 | Theoretical Flame Temperature | TFT | 3.107 * NCV | NCV | 6500 | |||

deg.C | SCA | SSCA | 9.28 | |||||

NCV | Net calorific value of fuel, kcal/kg-fuel | TFT | 2176 | |||||

SSCA | Specific stoichiometric combustion air, kg/kg-fuel | Target | – | |||||

8 | True CO2 in kiln exit gas | TCO2 | 100 * ( CO2 + CO ) | CO2 | 36.5 | |||

vol% | 100 + ( 1.89 * CO ) – ( 4.78 * O2 ) | CO | 0.002 | |||||

CO2 | Kiln exit gas CO2, vol% | O2 | 4.2 | |||||

CO2 | Kiln exit gas CO, vol% | TCO2 | 45.7 | |||||

O2 | Kiln exit gas O2, vol% | Target | – | |||||

9 | Burner Tip Velocity | BTV | 4 * Ps ^{0.5} | Ps | 1800 | |||

m/s | Ps | Static pressure in duct, mmWG | BTV | 170 | ||||

Target | – | |||||||

10 | %Primary Air | %PA | PA * 100 | PA | 2.05 | |||

% | SCA | SCA | 27.24 | |||||

PA | Primary air, kg/s | %PA | 7.53 | |||||

SCA | Stoichiometric combustion air, kg/s | Target | – | |||||

11 | Flame Momentum | FM | %PA * BTV | %PA | 11.2 | |||

or | %.m/s | %PA | %Primary air, % | BTV | 150 | |||

Relative Impulse | BTV | Burner tip velocity, m/s | FM | 1680 | ||||

(Source : F.L. Smidth) | Target | 1000-2000 |