High Momentum Design for Alternative Fuels Adriano Greco Ricardo - - PowerPoint PPT Presentation

High Momentum Design for Alternative Fuels

Adriano Greco Ricardo de Paula Costa

Alternative Fuels Benefits

• Cement plant point of view
• Cheaper kiln fuel resource
• Lower NOx emission
• Wastes elimination point of view (comparing to other

elimination methods)

• Utilize its heat capacity
• Full destruction of the material
• Do not have ashes (incorporated to the clinker)

Worldwide tr trend

3

Austria: >70% Germany: >60%

2015

Alternative Fuels – Latin America

Latin America: < 20%

Alternative Fuels used at at Cement In Industry

• Animal Meal
• Shreaded Plastics
• Wood chips
• Saw dust
• Biomass – husks
• Tires chips
• Fluff – municipal waste
• Chicken feathers
• Glycerin
• Textiles
• Solvents
• Sewage sludge
• Oil Sludge
• Cellulose, paper, board

Fir iring Alt lternatives Fuels

• Modern Kilns
• Start using calciner for AF firing
• Bigger particles sizes of AF
• High Substitution – Main Burner
• Old Kilns – No calciners
• Main burner
• Mid kiln tires firing
• Small portion in the kiln back

Alternative Fuels Sel electio ion

To be considered when firing AF:

• AF preparation
• Constant feed / conveying
• Chemical analysis - C, H, O, N, S, Cl
• Moisture, Volatiles
• Flame adiabatic temperature
• Refractory infiltration
• Sulfur balance
• Cl balance
• Presence of heavy metals P, Hg, Ti ...
• Lower clinker production (O2 and H2O)
• Maximum and Minimum particle dimension
• Shape of the particle

sphericity particle real

• f

area volume same the with sphere

• f

area   

Importance of particle shape:

COMBUSTION:

• Particles with lower sphericity have more surface area for the same

volume, i.e. they tend to present better heat and mass tranfer

• Particles with lower sphericity have lower terminal velocity, thus they have

higher “flying” time C (mm) L (mm) A (mm) Superficial area (mm2) Particle volume (mm3) Equivalent sphere area (mm2)  I 1.0 5.0 10.0 130.0 50.0 65.6 0.50 II 3.0 3.0 5.5 84.0 49.5 65.2 0.78

Combustion of

• f Soli

lid Was astes Overvi rview

• Unstable flame
• Wrong kiln thermal profile
• Higher kiln inlet temperatures
• Fuel falling onto clinker bed
• Reduction zone near clinker
• Excessive Sulphur recirculation
• Rings formation
• CO emissions
• Clinker quality
• Cement Strength
• Operational problems
• Environmental problems

When higher substitution rates are attempted with inadequate technology:

Fir iring Alt lternatives Fuels

Burners development

One or more pipes above the burner

• High oxygen zone
• Low control
• Low mixing
• Low oxygen zone
• High control
• High mixing

One or more pipes inside the burner

Old Concept New Concept

Hig igh Momentum Burner

Advantages of High flame momentum :

• Kiln operations becomes more stable & improved

fuel efficiency for hard to burn fuels

• Improved clinker reactivity and shorter sintering

zone

• Lowered volatility and recirculation of sulfur in kiln

gases (control of surfur into the clinker)

• Tendency for ring formation is lower
• Clinker granulometry more uniform

Requirement:

• 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

Combustion

SECONDARY AIR

• High oxygen availability: 95-100% of

required amount

• Low control and mixing
• Low velocity

PRIMARY AIR

• Low oxygen availability: 8-12% of

required amount

• High control and mixing
• Ignition fuel zone
• Flame stability

Combustion Secondary Air Secondary Air Primary Air Recirculated Gases

Lofting Air supply RDF Pipe – easily removable Axial Air Swirl Air Coal / Petcoke Igniter Flame Scanner Natural Gas Alternative Fuels Alternative Fuels With Lofting Air

Burner Concept

• Primary air pressure – 250 up to 650 mbar(g)
• Minimum coal/petcoke transport air - up to 5,0 kg/kg of air
• 8 to 12% of stoichiometric combustion air
• AF (solids) – with Lofting air
• Easy to burn AF – up to 4,0 kg/kg of air
• Hard to burn AF – up to 2,5 kg/kg of air

Axi xial l Air ir

• Mixing of the fuel and air occurs primarily as a result of jet entrainment

A free jet can entrain as much of the surrounding air until it’s velocity is the same as its surroundings and thus is able to expand unimpeded

U Um Uo r do Nozzle Potential Core Mixing Region Transition Region

Axi xial l Air ir

Air Assisted Dispersion of RDF and other similar fuels

Lofting Air supply RDF Pipe – easily removable Lofting air solid dispersion pattern

Loft fting Air ir

Effect of lofting air on volatiles burnout - RDF

Lofting air OFF Lofting air ON RDF volatiles mass fraction (coloured regions show RDF concentration) Burner tip Lofting air OFF Lofting air ON Flame temperature

The effect of lofting air on flame temperature map

Loft fting Air ir

Loft fting Air ir

Conclusion

• High Alternative Fuels Substitution requires a burner with high

momentum and good design in order to provide:

• Better mixture between secondary air and fuel;
• Better control of the flame envelope;
• Fast interation between the AF and O2;
• Good thermal flux.

Thank You