Flame Momentum

(1)

WELCOME

TO

BURNER TECHNICAL SESSION

(2)

AGENDA



 FLAME MOMENTUMFLAME MOMENTUM



(3)

AGENDA



 FLAME MOMENTUMFLAME MOMENTUM

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(4)

BURNER GENERAL ARRANGEMENT

(

(11) ) FFiirre e hhoooodd ((77) ) VVaallvve e ttrraaiinn (

(22) ) BBuurrnneer r sseeaall ((88) ) FFllaamme e ssaaffeettyy//ccoonnttrrool l ppaanneell (

(33) ) TTrroolllleeyy ((99) ) CCooaal l ttrraannssppoorrt t ssyysstteemm (

(44) ) IIggnniittiioon n ggaas s bbuurrnneerr ((1100) ) EEmmeerrggeennccy y aaiir r ffaan n ww//mmoottoorr (

(55) ) FFlleexxiibblle e ccoonnnneeccttoor r sseettss ((1111) ) PPrriimmaarry y aaiir r ffaan n ww//mmoottoorr (

(5)

BURNER DESIGN CONCEPT

Primary air inlet

Burner trolley

Burner pipe with refractory

(6)

BURNER FRONT END

Axial air channel

Radial air channel

Central air duct

(7)

INPUT DESIGN DATA

 Ambient pressure (mm Hg)

 Ambient temperature (



C)

 Kiln production rate (tpd)

 Firing in kiln (kcal/kg.cl)

 Fuel Net Calorific value (kcal/kg)

 Design coefficient coal (1.25)

 Coal conveying air amount (m³/min)

 Fuel flow rate (kg/h)

 Kiln hood width (kiln w.p.h to door front)

(8)

CONSTANTS USED IN DESIGN

 Axial air temperature: 80˚C

 Radial air temperature: 50˚C

 Coal transport air temperature: 70˚C

 Central duct air temperature: 50˚C

 Coal discharge velocity: 30 m/s

 Coal discharge velocity deviation: ± 2 m/s

 Max. radial air velocity: 30 m/s

 Max. axial air duct velocity: 35 m/s

 Central duct nozzle hole velocity: 20 m/s

 Refractory thickness: 80mm

(9)

CALCULATION

Burner capacity, Qmax (Mcal/h)

= (Design coefficient x Firing in kiln x kiln production)/24 Burner capacity (MW)

= (Qmax (Mcal/h) x 4.1868)/3600 Maximum fuel capacity (kg/h)

= (((Kiln production x 1000/24) x Firing in kiln) / Fuel NCV) x Design coefficient

(10)

CALCULATION

Theoretical air amount, Lmin (Kg/s)

= Burner capacity, Qmax (Mcal/s) x kg.air/Mcal

(Where 1.39 kg.air/Mcal > 4500 fuel NCV and 1.43 kg.air/Mcal < 4500 fuel NCV)

Primary air fan volume (m³/s)

= 10% of Theoretical air amount, Lmin / Ambient air density Absorbed power (kW)

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FLAME MOMENTUM

The best way of expressing the efficiency of a burner is by the momentum (primary air percentage multiplied by discharge velocity) expressed as %m/s or as n/mw (1 N/MW ≈ 296 %m/s).

The higher momentum means that a stronger, wider and shorter flame can be generated.

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PRIMARY AIR MOMENTUM

Input data:

Ambient pressure:

pamb



mbar



Ambient temperature:

tamb



C



Stoichiometric combustion airflow: Lmin



kg/s



Primary airflow, measured:

mpr



kg/s



Primary air pressure at nozzle:

pN



mbar



Primary air temperature:

tpr



C



Isentropic exponent for air:



1,4

(15)

PRIMARY AIR MOMENTUM

[ ]

%

100 min

´

=

L

pr

m

p

L

Primary air percentage:

Nozzle velocity:

(

)

[

m s

]

p p p t R c N amb amb pr pr 273,15 1 / 1 2 1 ú ú ú û ù ê ê ê ë é ÷÷ ø ö çç è æ + -´ + ´ -=

(16)

AIRFLOW CALCULATION

Input

data:-Nozzle area: AN [mm2]

Nozzle coefficient (for 100% axial air, lower with

swirl air) : kN

0,95

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AIRFLOW CALCULATION

(

)

(

)

k k k y 1 2 +

÷÷

ø

ö

çç

è

æ

+

-÷÷

ø

ö

çç

è

æ

+

=

N amb amb N amb amb

p

Flow function:

Primary air flow:

(

)

(

t

)

[

kg

s

]

R

p

k

A

m

pr N amb N N pr

/

15 ,

273

1

2

10

4

+

´

-´

+

´

=

-k k y

(18)

PRIMARY AIR MOMENTUM (EXAMPLE)

Input data:

Kiln production: 3949 tpd Ambient pressure: 953 mbar Ambient temperature: 43 °C

Stoichiometric combustion air flow, Lmin: 20.21 kg/s Axial air damper: 100% open Radial air damper: 20% open Nozzle coefficient: 0,95

Primary air pressure at nozzle: 197 mbar Primary air temperature: 80 °C

Air nozzle opening: 35 mm

Nozzle area: 7281 mm2

(19)

PRIMARY AIR PERCENTAGE (EXAMPLE)

199 ,

0

197

953

197

953

1,4 1 4 , 1 4 , 1 2



































 





_

_

kg s m_pr 132, / 15 , 273 80 89 , 286 1 1 4 , 1 4 , 1 2 197 953 199 , 0 95 , 0 7281 10 4



















%

53 ,

6

100

21 ,

20

32 ,

1

_

_



p

L

(20)

PRIMARY AIR MOMENTUM (EXAMPLE)

Velocity:

Primary air momentum:





m

s

c

_pr

193 /

197

953

1

15 ,

273

80

89 ,

286

1

4 ,

1

4 ,

1

2

1,4 1 4 , 1













































/s

m

G



6 ,

53 

193 

1260

%

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FLAME MOMENTUM EFFECT

Burner momentum is insufficient to effectively mix the fuel with the secondary air, the heat consumption could be increases.

Burner momentum is insufficient and it can give a lazy flame and a bad burn out of the fuel, which can lead to fuel particles in the charge The flame momentum below the recommended range will result in too long a flame, high kiln shell temperature above the burning zone and in the kiln back end as unstable kiln operation with a too long and cold burning zone thereby permitting undesirable clinker crystal growth.

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NOZZLE MOVEMENT

Minimum “0” Position Nozzle Flush Maximum Position Nozzle Retracted Adjustments made

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PRIMARY AIR MOMENTUM

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PRIMARY AIR MOMENTUM

(Nozzle min. open)

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PRIMARY AIR MOMENTUM

Fuel

gas

~1200

%m/s

Fuel

oil

~1200-1500

%m/s

Medium volatiles coal

~1500-1700 %m/s

Anthracite or petcoke

~1600-2100 %m/s

Secondary fuels, up to

~2400 %m/s

Flame Momentum is a practical number in which the flame shape will be optimum for the particular fuel.

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RADIAL AIR ADJUSTMENT

Open - more swirl action gives a recirculation zone resulting in shorter, wider and steadier flame

Close - less swirl action, long and relatively thin flame. Increase in radial air will results in a hot zone close to the burner.

For nominal operation, radial air damper will be set between 10 - 30 % open.

Excessive radial air might influence in coating loss close to the burner.

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RADIAL AIR EFFECT

Internal zone Hot secondary air Fuel and primary air Swirl air recirculation External recirculation zone

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AXIAL AIR ADJUSTMENT

Open - increases axial flow, relatively thinner and steadier flame.

Close - decreases axial flow, softer and less intense flame. Closing the axial air will make the flame softer / low

momentum and might result in the flame impingement on to the coating.

For nominal operation, axial air damper will be set 80 - 100 %open.

During startup, if there are fumes of un-burnt fuel (black and co formation) then it signifies either lack of axial air or the combustion air.

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AIR NOZZLE ADJUSTMENT

Open - rotating the spindle anti-clockwise will increases the nozzle area.

If the primary air fan damper control is in auto mode (static pressure), an increase in nozzle area will open the fan damper to maintain the static pressure thereby increasing the flame momentum.

Close - decreases in nozzle area will have a reverse effect of the above.

For nominal operation, nozzle position will be set between 45 -65 % open.