2. COMBUSTION REACTION
Combustion is a reaction between oxygen and fuel.
This oxidation is an exothermic reaction.
Correct proportion
OXYGEN FUEL
FLAME
Ignition
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3. BURNERS
OBJECTIVE: Insert fuel in the burning zone.
Its efficiency depends on the speed it enters in contact with
oxygen. They should be planned and regulated by way of
setting the heat in the ideal place, by way of not causing
damages to the wall (refractory) and to produce as less
pollutants and possible (CO, NOx, SO2).
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4. Rotary Kiln Burner & Flame Theory
Function of a rotary kiln burner:
• Mix fuel and combustion air to produce a stable flame and to release heat in a way adapted to process requirements.
Diffusion flames:
• Burner fed with 100% of the kiln fuels but only ~10% of required combustion air (Primary Air). The other 90% of combustion
air comes from the cooler (Secondary Air), to recover the material energy. Thus, with only 10% of the combustion air, the
burner must be able to produce:
An adjustable thermal profile
A stable flame:
Efficient combustion & Reduced air emissions
Impulse (Momentum):
• Force generated by the primary air and fuels discharge
velocity at the burner tip.
Impulse (N) = Mass flow (kg/s) x Velocity (m/s)
• It generates the secondary air and the fuels mixing.
• Proportional to the heat release: Specific Impulse (N/MW) C
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Peers Conference 2019 – Rotary Kiln Burner
5. Single stage burners
Unique duct to:
Fuel + primary air
Usually used for short kiln. They can be used for fuel
simultaneously with other fuels, and in this case they have to
be equipped with an extra pipe in the centre of the duct.
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Coal and/or pet cock
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6. Multi-stage burners
For a more efficient adjustment in the flame, through
primary air, multi-stage burners are used, which are divided
in two components, axial and radial, with the fuel being
introduced also through a tube which is concentric with
others.
They can be used for only one fuel or for several alternately
or simultaneously (gas, liquid or solid).
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transport
swirl
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Axial air is injected towards the kiln axel.
The swirl air is injected towards the kiln burner (the angle is
one of the burner’s project parameters) .
Multi-stage burners
The swirl component of radial air creates a rotating air flow
around the kiln (like a screw), which also pushes in towards
the exterior.
As the swirl air is located internally to the axial air, its
increase causes flame enlargement.
21. Edição:01 Firing 170
Swirl Air
Axial Air
Pet coke
ASB
Animal Meal
Used oils
Central Ar
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LAFARGE BURNER
22. Independent ring jets, with
nebulization per auxiliary fluid
(compressed air or vapour); open
chamber type nozzle.
Burner with three adjustment air ducts.
Each ring for solid fuel and central duct
for the alternative solid fuel.
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GRECO Burner
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23. DESIGN OF
FLEXIFLAME
BURNERS FOR
PETCOKE
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EXTERNAL AIR
TANGENTIAL AIR (ROTATION)
COAL/PETCOKE
DISPERSION AIR (ROTATION)
CENTRAL AIR
(RECIRCULATION/COOLING
SLUDGES / ANIMALMEAL
IGNITOR
MIXING AIR FOR ASF
RDF / FLUFF
DOUBLE SWIRL EFFECT
26. Peers Conference 2019 – Rotary Kiln Burner
Fives Pillard Rotaflam® Burner – Multichannel Burner
Adjustable tips cross section during operation
Independently adjustable primary air & natural gas
pressure & flowrates
2. Central stabilizer
Improved flame stability (bluff body = internal recirculation)
Possibility for integrated warm-up burner for gaseous or liquid
fuel
Possibility for integrated igniter & flame detection
Possibility for integrated lance for solid, liquid or gaseous fuels
3. Fuel concentration for NOx reduction
Fuel injection inside primary air
Low O2 content at flame core
Rotaflam® Multichannel Burner
1. Adjustable Axial air, Radial air & Natural Gas tips
Flame shaping:
HFO / NG / Biogas / NCG / Petcoke HFO / Methanol – Ignitor trial
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27. Peers Conference 2019 – Rotary Kiln Burner
Fives Pillard Rotaflam® Burner – Main Characteristics
Coal / Petcoke /
Anthracite / Lignite
Central stabilizer
• ASF / ALF / HFO / DO
• Ignitor / Flame detection
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Axial primary air
Adjustable cross section
Radial primary air
Adjustable cross section
Natural gas
Adjustable cross section
28. Peers Conference 2019 – Rotary Kiln Burner
Fives Pillard Rotaflam® Burner – Main Characteristics
Axial & Radial air pressure control
Axial air tip
adjustment
Radial air tip
adjustment
Natural gas Coal
Cooling air
Axial air
Radial air
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29. Peers Conference 2019 – Rotary Kiln Burner
Fives Pillard Rotaflam® Burner – Adjustable momentum principle
Axial tip: CLOSED (minimum section)
Air flowrate: REDUCED
Momentum: REDUCED (for similar pressure)
Slot effect for higher sec.
air absorption efficiency
Axial tip: OPEN (minimum section)
Air flowrate: INCREASED
Momentum: INCREASED (for similar pressure)
Slot effect for higher sec.
air absorption efficiency
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30. Peers Conference 2019 – Rotary Kiln Burner
Fives Pillard Rotaflam® Burner – Adjustable momentum principle
Stroke: + 35 mm
Axial tip
CLOSED
Stroke: + 35 mm
Radial tip
CLOSED
Axial tip
OPEN
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31. Pellet
Secondary circuit
Primary atomizer
Secondary atomizer
Primary circuit
Fuel
Liquid fuel injection
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Objective:
Mix the fuel with primary air;
Achieve the atomization adequate for the fuel;
EXAMPLE I: mechanical atomization (diagram MY)
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Ignition moment impact in the flame
(Rotaflam Burner, Coal with medium volatile material)
02 Jan 2006
High Swirl, low axial moment Low swirl, high axial moment
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Images ECRA
33. Is = 9
Swirl = 0.15
Strong and
narrow flame
Images Lafarge
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Is = 6
Swirl = 0.15
Normal
Flame
Is = 3
Swirl = 0.15
Lazy
Flame
Is = 6
Swirl = 0.25
Strong and
large flame
Is = 6
Swirl = 0.15
Normal
Flame
Is = 6
Swirl = 0.05
Long and
narrow flame
Effect of the moment and of the swirl in the
shape of the flame
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34. Alignment of the burner in the kiln
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The burner should always be aligned with the kiln axel.
If it is in the horizontal, as the kiln axle is at
approximately 3º, the flame touches the materials,
creating local reduction conditions, thus causing the
increase of alkalis and sulphur volatilisation.
35. Fuel characteristics
As mentioned in the beginning of the chapter, the characteristics
and the fuel preparation level limit the shape and length of the
flame.
Volatile content (MV):
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Ignition time and distance
MV =>
Fineness :
Fineness => Ignition time and distance
Ash content:
Ashes => Ignition time and distance
Ashes absorb heat
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36. Mixing different fuels, as for example natural gas with fuel or
coal, makes alterations in the flame length. Besides, it changes
the maximum temperature position as well as the heat transfer
by radiation (different emissions):
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The flame length is superior to when only one fuel is burnt.
(The necessary air mixes itself more quickly with a fuel, thus
reducing combustion time).
Changing fuel or burning a fuel mixture demands an adequation
of the burner parameters, in order to avoid flame alterations.
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Fuel mixture effect
37. 70% Coal
30% Pulverised WTC Mud
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100 % Coal
Fuel mixture effect
(Rotaflam Burner, high swirl / medium axial moment)
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38. Flame adjustments
Follow the supplier’s instructions;
Adjust parameters only when the kiln is stable;
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Make progressive adjustments of one parameter at a time (eg:
axial air or swirl air) and monitor combustion indexes;
Attention:
1) The kiln takes long to react, so time should be given
between alterations to verify exactly what the consequences
are;
2) Axial air is also used to cool the pipe, so it should never be
regulated below a certain level.
40. DESIGN OF
FLEXIFLAME
PETCOKE
Combustion of petcoke:
Petcoke is harder to ignite as conventional coal (low volatile)
Petcoke provides a higher flame radiation then coal
Petcoke has a typicall high sulfur content
Petcoke develops a higher NOx formation
Usually petcoke changes the kiln profile
Petcoke needs a special burner design
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41. PETCOKE
COMBUSTION
The combustion of petcoke requires:
Quick mixing of secondary air to the flame, to allow the complete
combustion which is iniciated by primary air.
Primary air jets need to accellerate the secondary air.
Internal recirculations are controlling the ignition distance of the fuel
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42. Peers Conference 2019 – Rotary Kiln Burner
Atomizing steam pressure
Atomization quality vs. Flame intensity (Lime Reburning Kiln)
NOx (mg/Nm3 at 7%O2)
Lower atomizing steam pressure means bigger droplets, longer and
less intense flame (lower peak temperature, lower NOx)
Fives Pillard Rotaflam® Burner – Liquid Fuel Injectors
The key parameter for a proper liquid fuel combustion is the
atomization quality.
The size of the fuel droplets will determine how fast it will burn
and how far it will go. Thus, it is possible to change the flame
length and shape by changing the atomization quality.
Assisted Atomization (steam or compressd air)
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