2. Burner Design Criteria

BU R NE R DE SI G N C R I TER TERII A 

Theoretical combustion air required Hu= (Kj/kg)/4.19*1000 +0.5505 Hu (=CV of fuel) (as per Atto Labahan)



Emperical eqn for theoretical air required / 1000 cv = 1.05 Nm3/kg (solid fuel) = 1.10 Nm3/kg (liquid fuel) = 1.15 Nm3/kg (gaseous fuel)

BU RNE R DE SI GN CRI TERI A



Theoretical combustion gases = Theoretical air required * 1.07



CO2 generated from raw mix = 0.27  –  0.29 Nm3/kg (depending on the total carbonate content)

F L AM E SH APE D EPEND S



Percentage Primary Air



Primary Air Velocity



Mixing of Coal & Air



Flame Momentum  –  Depend on Percentage Air & Primary Air Velocity



Secondary Air Velocity



Secondary Air Temperature

F L AM E SH APE D EPEND S



Recirculation



Primary Air Velocity / Secondary Air Velocity Ratio



Burner Dia / Kiln Dia ratio



Burner Position



Excess Air

EF F ECT OF PERCEN TAGE OF PRI M ARY AI R 





Higher the percentage Primary Air, higher the Heat Consumptions in Kiln. 1% increase of Primary Air, Heat Consumption increase by 4 kCal/Kg Clinker. Percentage Primary Air can be even 6%. 2% on Transport Air & 3 to 4% as Axial Air & Radial Air. Radial Air generally 30% & Axial Air 70% for a good flame shape.

EF F ECT OF PERCEN TAGE OF PRI M ARY AI R 6 % Primary Air

2% Transport Air

4% (Axial Air + Radial Air)

1.2% Radial Air

2.8% Axial Air

PRI M ARY AI R VEL OCI TY 

Flame length decreases with higher Primary Air velocity & then again it increases with increase of Primary Air velocity.

Flame Length

Optimum Flame length vis-a-vis velocity Velocity of Primary Air

Velocity of coal tip = 30 m/sec  Velocity of radial air tip = 90  –  130 m/sec = 140  210 m/sec  Velocity of axial air tip 

M I X I N G OF COA L & A I R For a good flame, it is essential that coal & air has to be mixed thoroughly. Better is the mixing, better is the flame.  Swirler in radial air line & coal line have to be in opposite direction for better mixing. 

Axial Coal Radial Radial Coal

F L A M E M OM E N TU M



Flame momentum = % PA x (Velocity)2  1,00,000  –  1,20,000







Flame momentum has more influence by velocity of Primary Air than % PA. As percentage Primary Air decreases, the velocity has to be increased to satisfy the flame momentum. For 6% PA, the velocity of Axial Air is required 130  –  140 m/sec.

SECON D ARY AI R VE L OCI TY



Secondary air velocity should be in the range of 4  –  5 m/sec.



More the secondary air velocity inside the Kiln, more dust carryover into Kiln.



It leads wear / tear on tip casting back.



It creates a dust envelope around the flame & flame temperature goes down.

SECON D ARY AI R TE M PERATU RE



Higher the secondary air temperature, higher is the flame temperature for same quantity of secondary air.

Flame Temp.

2200°C 2000°C 1800°C

1000°C 900°C 800°C Secondary Air Temp. °C

SECON D ARY AI R TE M PERATU RE



Secondary air temperature has to be measured

 just above the clinker bed height. 

Secondary air temperature can be increased by 200°C due to full height of clinker from cooler.

RECIRCULATION





For a good flame recirculation of air & coal is a must. Better is the recirculation, better formation & stability of flame. ) ) )

)

)

)

)

)

)

) )

) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) )

)

)

)

)

)

) )

) )

) )

RECIRCULATION





High velocity of primary air creates a sudden vacuum & leads to recirculation. At the time of recirculation, mixing with secondary air temperature& quantity is important.

PRI M ARY AI R / SECON D ARY AI R VEL OCI TY RATI O 





Up Us

should be in the range of

25 ~

35

Lower Up/Us < 25, lower is the recirculation & inferior is the flame. Higher Up/Us > 35, heavy high recirculation & unstable flame shape. Where:  Up

Primary Air Velocity, m/sec

 Us

Secondary Air Velocity, m/sec