Biomass Combustion in Europe Thomas Nussbaumer Lucerne University - - PowerPoint PPT Presentation

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Biomass Combustion in Europe Thomas Nussbaumer Lucerne University of Applied Sciences 6048 Horw Verenum R&D in Bioenergy 8006 Zurich SWITZERLAND EMEP, Albany (NY), USA 11.16.07 Verenum Biomass Combustion in Europe 1. Introduction 2.

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SLIDE 1

Biomass Combustion in Europe

Thomas Nussbaumer Lucerne University of Applied Sciences 6048 Horw Verenum R&D in Bioenergy 8006 Zurich SWITZERLAND

Verenum EMEP, Albany (NY), USA 11.16.07

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SLIDE 2

Biomass Combustion in Europe

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions

Verenum

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SLIDE 3

The fossil Period: A Peak in History

Verenum

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SLIDE 4
  • 1. Heat
  • 2. Power
  • 3. Transport ?

!

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SLIDE 5

Carbon C cle for Bioener

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CO2 Ca, K, ... C, Ca, K, N

CO + Corg + Cel NOx+N2 hν KCl, CaCO3

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SLIDE 6

Sustainability Requirements for Bioenergy

  • 1. Sustainable biomass production:

No deforestation !

  • 2. Social aspects:

Biomass for food first, no competition

  • 3. Ecological aspects:

Acceptable air pollution

Verenum

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SLIDE 7

Biomass Combustion in Europe

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 8

Flame Principles

Verenum

Kerze mit und ohne Russ Gasfeuerzeug Kerze in Glas: Wandtafel mit Molekülen: Neue Stoffe entstehen, Beweis: Kerze mit schwarzem Russ

Diffusion Flame Premixed Flame

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SLIDE 9

Wood Combustion with Air λ = Excess air ratio = Air/Airstoch = O2 / O2 min

CH1.4O0.7 + λ (O2 + 3.76 N2)

–> Intermediate Products (CO, H2, CmHn,...)

CO2 + 0.7 H2O + (λ–1) O2 + λ 3.76 N2

+ 18.3 MJ/kg

Verenum

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SLIDE 10

100000 10000 1000 100 10 1 10 100 1000 10000

HC CO

[mg/m3] [mg/m3]

HC und CO in [mg/m3] bei 11 Vol% O2

a b c

Correlation between CO and Hydrocarbon (HC)

Open Chimney Log Wood Boiler Automatic Wood Chip Boiler (under stoker) [Nussbaumer 1989] Verenum

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SLIDE 11
  • mb. chamber

at extraction > 0.5 s

Requirements for Complete Burnout: T T T

Temperature – Time – Turbulence (Mixing)

> 850°C

  • co

(dry wood )

  • he

λ

< 2

2-stage Comb. with primary & secondary Air Ventilator Mixing zone Re > 2300

Verenum

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SLIDE 12

T (λ) Influence of excess air on Temperature Excess air ratio T (λ) dry wood

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SLIDE 13

Group of Pollutants from Wood Combustion

CH1.4O0.7 + O2 → CO2 + 0.7 H2O N K, Ca, Na, Cl 1 2 3 → CO, CXHY, Corg, soot ... → NOX , S..→ KCl, K2SO4, CaCO3 ...

PM

Verenum

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SLIDE 14

Biomass Combustion in Euro e

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 15

1-stage combustion

Air

C H O + Air O2 + N2 at λ > 1 CO2, H2O, O2, N2 CO, CxHy Verenum

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SLIDE 16

CO (λ) Influence of Excess Air Lambda on CO

Verenum

1-stage combustion

Eta (λ)

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SLIDE 17

Limitations of 1-stage Combustion

Problem 3: Air Leakage Problem 6: Flame Quenching Problem 5: Heat Extraction in Combustion Zone Problem 4: Gas Leakage Problem 2: Mixing Air + Gas Problem 1: Air Distribution

Verenum

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SLIDE 18

1-stage Combustion Wood Stove

Verenum

Eta < 60%

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SLIDE 19

Verenum

Organic PM / Tar Soot

[Kägi & Schmatloch 2002]

Heuberger in [Klippel & Nussbaumer 2007]

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SLIDE 20

1-stage Combustion with Combustion Chamber Air

Verenum

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SLIDE 21

Biomass Combustion in Euro e

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 22

Verenum Hoval Hoval

2-stage Combustion with forced Downdraft

Wood: C H O CO, H2, CxHy CO2, N2 + Air λ > 1 O2 + N2 CO2, H2O, N2 + Air λ < 1 O2 + N2

Eta > 90% – Heat Storage

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SLIDE 23

2-stage Combustion with forced Downdraft

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Premixed flame

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SLIDE 24

2-stage Combustion with Downdraft and Grate

Schmid Verenum

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SLIDE 25

Combustion control

CO (λ) Influence of Excess Air Lambda on CO

Verenum

Simple wood stove Furnace with 2-stage combustion

  • Autom. furnace 2000

Pellet furnace

  • Autom. furnace 1990

Downdraft boilers are sensitive for channelling and bridging –> not suited for fine wood (dust) or very large logs !

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SLIDE 26

Verenum

Detail of stove 3

Tiba (Switzerland) Prototype 2-stage Stove

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SLIDE 27

Verenum

2-stage Combustion Stove in Operation

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SLIDE 28

Pellet Boiler with Automatic Ignition

Verenum

Hargassner (Austria)

Eta > 90%

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SLIDE 29

Pellet Boiler with Grate for periodic Ash Removal

Verenum

Liebi LNC AG (Switzerland)

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SLIDE 30

Under Stoker Boiler Grate Boiler

Verenum

w ≈ 10% – 50%, a < 5% w ≈ 10% – 55%, a < 50%

200 kW ... 2 MW 400 kW ... >10 MW

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SLIDE 31

Under Stoker Boiler 200 kW ... 2 MW Grate Boiler

w ≈ 10% – 55%, a < 50%

400 kW ... >10 MW

Schmid (Switzerland) Verenum

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SLIDE 32

District Heating 6.4 MW

Schmid AG, Wilderswil, Interlaken (Victoria-Jungfrau) Verenum

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SLIDE 33

NO+NH2 →N2+H2O

T T T: Time, Temp., Turbulence

  • Mixing limits burnout
  • Excess air low (1.5) and

accurately controlled Burnout quality

[Bruch & Nussbaumer, 1998] Verenum

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SLIDE 34

Verenum

Combustion Modeling

Verenum

[Bruch & Nussbaumer, 1998]

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SLIDE 35

Fluid Dynamics: Model Laser Camera

Verenum [Brzovic, Nussbaumer & Baillifard, 2007]

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SLIDE 36

Biomass Combustion in Europe

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 37

Particle Measurement

Verenum

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SLIDE 38

Ver leich der Toxizität verschiedener Partikel

Verenum

6 7 8 4 3 1 8

5

2

Wood stove with bad operation Wood soot and tar ( condens.)

Toxicity = 10

Diesel soot Diesel car without particle filter Automatic wood furnace Ash particles = salts

Toxicity = 1 Toxicity < 0,2

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SLIDE 39

Results of Cytotoxicity Tests

Verenum

Cell Survival

10 20 30 40 50 60 70 80 90 100 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Particle concentration in cell medium [g/ml] Survival [%]

Diesel soot Inorganic particles (AWC) Similar for empty filter !

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SLIDE 40

Results of Cytotoxicity Tests

Verenum

Cell Survival

10 20 30 40 50 60 70 80 90 100 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Particle concentration in cell medium [g/ml] Survival [%]

Diesel soot

particles from bad combustion conditions in a small wood stove

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SLIDE 41

Origin and detection of PM from biomass combustion

Salts Soot Tar Origin solid Form

+

Filter at 180°C (VDI)

(+)

Impinger after filter (EPA) Ash Incom- plete com- bustion liquid

– +

Verenum

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SLIDE 42

Salts 100 < 20 Soot < 5 < 20 100 5 000 Tar < 5 < 5 400 10 000 Total PM

Verenum

< 100 < 50 500 15 000

Typically

  • perated

wood stove Ideally

  • perated

wood stove Badly

  • perated

wood stove Automatic wood combustion

Typical Emissions (mg/m3 @ 13 Vol.-% O2 )

mg/MJ = 0.68 x mg/m3

@ 13 Vol.-% O2

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SLIDE 43

Particle precipitation

Pre dedusting > 5 µm Fine particle removal < 10 ... < 0,01 µm

Cyclone Electrostatic Precipitator (ESP) Fabric filter (FF)

– +

Clean gas

+

Raw gas Condensation! C-content < 2%

Verenum

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SLIDE 44

– + +

Scheuch

Particle precipitation

Pre dedusting > 5 µm Fine particle removal < 10 ... < 0,01 µm

Cyclone Electrostatic Precipitator (ESP) Fabric filter (FF)

Aerob-Beth

Raw gas Clean gas

Scheuch

Condensation! C-content < 2%

Verenum

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SLIDE 45

Biomass Combustion in Europe

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 46

Conversion of Fuel-Nitrogen

N

in Fuel

  • NH2

NO O2 N2 O2 HCN NH3 Temp

Verenum

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SLIDE 47

λ = 0.7 NO+NH2 →N2+H2O

[Keller & Nussbaumer, 1994] , 2001] [Salzmann & Nussbaumer

Verenum

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SLIDE 48

Air staging

Verenum Müller Vyncke

Air staging and Fuel staging

Reduction zone

[Salzmann & Nussbaumer, 2001] [Fastenaekels & Nussbaumer, 2002]

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SLIDE 49

Biomass Combustion in Europe

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 50

PCDD/F as a function of carbon burnout

[Oehme et al. 1987] Verenum

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SLIDE 51

Biomass Combustion in Euro e

Verenum

  • 1. Introduction
  • 2. Fundamentals
  • 3. One-stage combustion
  • 4. Two-stage combustion for high burnout

a) Log wood, b) Pellets c) Automatic Boilers

  • 5. Particle emissions
  • 6. NOX emissions
  • 7. Other pollutants
  • 8. Conclusions
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SLIDE 52

Conclusions (1/2)

  • 1. Biomass combustion exhibits a relevant potential
  • 2. Efficiencies of > 80% are achievable in small and

medium scale

  • 3. Wood combustion can cause PM, PAH, CO, VOC
  • 4. Wood combustion is a major source of organic PM today
  • 5. PM consists of salts (s) soot (s) & organic condensables
  • 6. Salts from automatic plants are less toxic than soot and

can be reduced by secondary measures

  • 7. Soot and organic condensables are highly toxic and

need to be reduced from manual combustion

  • 8. Two-stage combustion at optimum excess air ratio

thanks to ideal operation and/or advanced combustion control enables high combustion quality

Verenum

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SLIDE 53

Conclusions (2/2)

  • 1. Wood stoves and old or simple wood boilers often

– exhibit no real two-stage combustion – exhibit too small combustion chamber if filled – miss heat storage – are not capable to be operated at part load after filling – can be operated with lack of oxygen

  • 2. An environmentally friendly use of wood in residential

applications is a huge challenge and needs improvement in technology, application, and regulation

  • 3. All other fuels than natural wood (agricultural biomass,

waste) can lead to significantly higher air pollution, i.e., PM, NOX, HCl, PCDD/F, heavy metals) and need to be restricted to large plants with flue gas cleaning

Verenum

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SLIDE 54

Acknowled ments

Acknowledgments

Swiss Federal Office for Energy Swiss Agency of the Environment

Thomas Nussbaumer, Switzerland – University of Applied Sciences Lucerne – Verenum Zurich www.verenum.ch

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