A new technology for high efficient Waste-to-Energy plants€¦ · 3 H. Hunsinger - ICIPEC 2010 Institute for Technical Chemistry - ITC-TAB Today more than 70 MSWI plants Total incineration

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association www.kit.edu

Karlsruhe Institute of Technology (KIT), Campus NordInstitute for Technical Chemistry – Thermal Waste Treatment DivisionPostfach 3640, D-76021 Karlsruhe, GermanyE-mail: [email protected]

A new technology for high efficient Waste-to-Energy plants

Hans Hunsinger

Institute for Technical Chemistry - ITC-TAB2 H. Hunsinger - ICIPEC 2010

Municipal waste management in Germany

18.3

20.3

20.1

21.1

20.7

21.9

22.5

22.4

22.8

24.9

29.0

34.0

33.6

34.5

22.6

22.9

27.5

27.2

35.7

35.9

35.4

41.8

43.3

41.0

45.5

48.0

49.0

47.9

0%

20%

40%

60%

80%

100%

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

compostingrecyclingincinerationlandfill

Municipal waste management in EU27

0%

20%

40%

60%

80%

100%

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

compostingrecyclingincinerationlandfill

Germany: Landfill ban: 1st of June 2005Landfill limit: TOC <1%

Data source:

no landfill of untreated waste

Strategy of waste management in EU27 and Germany

• Avoidance of land filling of untreated waste• Increase of recycling and material recovery • Environmentally sound and high efficient energetic utilization of the residual waste


Today more than 70 MSWI plants Total incineration capacity of 20.3*106 tons per yearAvg. LHV of municipal waste ≈ 10 MJ/kgEnergy content of annually burnt municipal waste ≈ 56.4 TWh

Efficiency of energetic utilization at German MSWI plantsheat utilization ≈ 27% (average, all plants)

net efficiency of power generation ηel. ≈ 10% (average, all plants)

net efficiency of power generation ηel. ≈ 18% (modern plants)

Situation of MSW incineration in Germany

50-60% of the total MSW-carbon is biogenic originsignificant renewable energy source ≈ 30 TWh


Examples of power generation efficiencies of advanced solid fuel combustion processes

10

15

20

25

30

35

40

45

50

350 400 450 500 550 600 650steam temperature (°C)

elec

tric

effic

ienc

y (%

)

Nordjylland/DK290bar/580°C76bar/580°C19bar/580°C

MSW (grate)AVI Amsterdam/Nl130bar/440°C14bar/320°C

RDF (grate)Rüdersdorf/D90bar/420°C23bar/420°C

modern grate MSWI40bar/400°C

1x intermediate superheating

no intermediate superheating

2x intermediate superheating

MSW , sewage sludge, biomass (grate)Brescia/IT 61bar/450°C

CFB

grateCFB

MSW/RDF Biomass Coal


Boiler corrosion in MSWI limits max. steam temperature

0 200 400 600 8000 200 400 600 800

corrosionbelow ash deposits

(chlorides)

corrosion of gas phase

acid dew pointcorrosion

boiler wall temperature °C

corr

osio

n ra

te

low corrosion

Chloride rich ash deposits on the boiler surface cause chlorine induced corrosion strongly increasing with temperature

Economic compromise of maintenance costs and power generationsteam Tmax. ≈ 400°C

Seier, J., Albert, F.: VDI-Berichte 1390, (1997), S. 349 -358

current design of MSWI:


Evaluation of new WtE processes upgrading the steam temperature

corrosion-resistant boiler material(Inconel®-Cladding)

corrosion-resistant boiler material(Inconel®-Cladding)

steam temperature

Chemical inhibitation of boiler corrosion (SO2-rec. process)

Chemical inhibitation of boiler corrosion (SO2-rec. process)

Combined steam cycles of MSW with fossil fuel fired power plants

Combined steam cycles of MSW with fossil fuel fired power plants

440 - 460°C >500°C

extra super heater at low corrosive locations

- sand loop of CFB) - divided combustion chamber in grate furnace

extra super heater at low corrosive locations

- sand loop of CFB) - divided combustion chamber in grate furnace

Waste (RDF) gasification(cleaned syngas combustion)

Waste (RDF) gasification(cleaned syngas combustion)

≈ 400°C

modern grate MSWI

modern grate MSWI


Measures for maximized electricity generation from MSWI

• High temperature steam generation at low boiler corrosion

• Intermediate steam reheating (high/low pressure steam cycle)

• Low pressure/temperature of steam condensation (no heat utilization)

• Regenerative condensate preheating

Minimized heat lossMinimized heat loss

Optimization of the Rankine cycle approach to Carnot efficiency

Optimization of the Rankine cycle approach to Carnot efficiency

• Low excess air combustion

• Low flue gas temperature at boiler exit

Low energy consumption of the plant

Low energy consumption of the plant

• Avoidance of pollutant formation (NOx, PCDD/F reduced efforts in flue gas cleaning)

• Low quantity and good quality of residues (TOC, PAH) like in modern MSWI (no residue treatment)


T (°

C)

0

200

400

600

800

1000

C (%

)

0

20

40

60

80

100

O2 (

Vol.%

)

0

5

10

15

20

25

Characteristics of MSW combustion in a grate furnace

zone 1 zone 2 zone 3 zone 4

primary airfuel bed

TO2

C

drying pyrolysisgasification fixed carbon burnout

λ>1λ<1λ>1bottom ashMSW

grate


Characteristics of MSW combustion in a grate furnace

zone 1 zone 2 zone 3 zone 4

primary airfuel bed

drying pyrolysisgasification fixed carbon burnout

λ>1λ<1λ>1bottom ashMSW

flue gas burn out zone

secondary air

flue gas λ>1steam boiler

λ<1 λ<1


Example: Low calorific MSW: LHV≈7.4MJ/kg

Axial O2 profile in the flue gas above the grate over the grate length at different excess air ratios

0

5

10

15

20

25

0.6 0.8 1.0 1.2 1.4 1.6

O2 (

Vol.%

wet

)

grate length

λpprimary air stoichiometry λp

O2


Products of uncompleted combustion (PICs)

0.0

0.5

1.0

1.5

2.0

2.5

0.6 0.8 1.0 1.2 1.4 1.6

soot

(g/m

3 wet

)

grate length

λp

0

2

4

6

8

0.6 0.8 1.0 1.2 1.4 1.6

CO

(Vol

.% w

et)

grate length

λp

0

10

20

30

40

0.6 0.8 1.0 1.2 1.4 1.6

CnH

m (g

/m3 w

et)

grate length

λp

0.0

0.5

1.0

1.5

2.0

2.5

0.6 0.8 1.0 1.2 1.4 1.6

H2 (

Vol.%

wet

)

grate length

λpPrimary air stoichiometry λp Primary air stoichiometry λp

Primary air stoichiometry λp Primary air stoichiometry λp

CO

H2CnHm

Soot particles


At λp ≤0.8 flue gas shows heating values up to 3 MJ/m3 at the O2 minimum

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.6 0.8 1.0 1.2 1.4 1.6

LHV

(MJ/

m3 w

et)

grate length

λpPrimary air stoichiometry λp

LHV (only gaseous compounds)

Axial profile ofLHV in the flue gas above the fuel bed

Example: Low calorific MSW: LHV≈7.4MJ/kg


soot

par

ticle

s

CnH

m

met

hane

ethe

ne

ethy

ne

benz

ene

tolu

ene

naph

thal

ene

phen

anth

rene

anth

race

ne

fluor

anth

ene

pyre

ne

pyrid

ine

0.001

0.01

0.1

1

10

100

C2H

2

CH

4

C2H

4

C6H

6

C7H

8

C10

H8

C14

H10

C14

H10

C16

H10

C5H

5N

ΣC

nHm

soot

C16

H10

average

Volatile org. compoundsgas phase

Low volatile PAHmainly adsorption on

soot particles

Con

cent

ratio

n (g

/Nm

3 , dr

y)Concentrations of organic compounds in the flue gas above the grate at the main combustion zone


German regulation for underground disposal (VersatzV 2002)TOC ≤6%, ΣEPA16 PAH <20mg/kg

Concentration of TOC and PAH in ash particles collected by filtration of the fuel gas at the main combustion zone

0

10

20

30

40

50

60

70

TOC

TOC

con

cent

ratio

n (%

)

No disposal of gasification ash possible, treatment necessary!

1

10

100

1000

10000

phenan

threne

anthrac

ene

fluor

anthen

e

pyrene

PAH

con

cent

ratio

n (m

g/kg

)

German regulation

German regulation

ΣEPA16 PAH <20mg/kg

TOC ≤6%


Release of corrosive elements and HCl in the flue gas above the fuel bed

Example: Low calorific MSW: LHV≈7.4MJ/kg at λp ≈0.75


grate zones

NO

, NH

3 (m

g/N

m3 )

0

500

1000

1500

2000

2500

O2 (

Vol.

%)

0

5

10

15

20

25

O2

NH3

NO

Concentration of N-compounds in the flue gas above the fuel bed

Hunsinger et al., 5th i-CIPEC, 16-19 December 2008, Chiang Mai, Thailand


• Calorific value (LHV) is sufficiently high for separate energetic utilization (= fuel gas)

• Raw fuel gas contains corrosive compounds and pollutants

• Volatile corrosive chlorides (Pb, Zn, K, Na etc.) • HCl, H2S• Ash particles

• Volatile corrosive chlorides (Pb, Zn, K, Na etc.) • HCl, H2S• Ash particles

Summary of flue gas characterization at the main combustion zone (O2-Minimum)

removal prior energetic utilization

• NH3• NH3

to be burnt (after separation)

should be converted to N2 (minimizing NOx formation)

• soot particles and adsorbed CnHm (PAH)


gasification ash(chlorides, soot, PAH)

+ CaCl2air

2) Hot gas filtration + dry sorption of HCl (H2S)

3) Combustion of the cleaned fuel gas

4) Heat utilization for steam super heating

Ca(OH)2

Raw fuel gas

air

Flue gas

≈900°C

1) Cooling to T≈400°C(Condensation of volatile chlorides, avoiding tar condensation)

Fuel gas cleaning and energetic utilization

NOx


Raw gas

Water-/steam cycle

Main furnace

Primary air

Flue gas

Emission

Steam generator

Steam turbine

Condenser

Economizer

Super heater

Evaporator

Secondary air

Flue gas cleaning

Qel.

p=40bar/T=400°C

Bottom ashstandard process scheme

Flue gas burnout

Solid fuel burnoutFuel

λ<1

λ>1


ash(soot) + CaCl2

Raw gas

Water-/steam cycle

Main furnace

air

Primary air

Flue gas

≈400°C

Emission

2) Hot gasfiltration

+ dry sorptionSteam

generator

3) Secondarycombustionchamber

Steam turbine

Condenser

4) Superheater SH2

Economizer

Super heater SH1

Evaporator

Secondary air

Ca(OH)2

Flue gas cleaning

Qel.

1) Heatexchanger

p=120bar/T=540°C

T=400°C

Fuel gas

air

Bottom ashscheme of new process

Flue gas burnout

Solid fuel burnoutFuel

(MSW) Bypass flue gasλ<1

λ>1

Bypass process

p=120bar

≈900°C

≈600°C


Reduction of pollutants

Ash from fuel gas filtration• TOC and PAH are burned when feeding back into the combustion chamber of the

main furnace (prior secondary air supply)• Heavy metals, chlorides and formed HCl will be collected in the flue gas

cleaning system of the main furnace

• NH3 in the fuel gas forms NOx during combustion in the bypass furnace

• NOx will be destroyed when injecting the by-pass flue gas back into the reducing atmosphere of the main furnace prior secondary air supply

4NO + 4NH3 + O2 4N2 + 6H2O2NO + 2CO N2 + 2CO2

Flue gas of the bypass combustion process

Re-burn

SNCR


p=40

bar

T(°

C)

s (kJ/kg K)

T=400°C

Wet steam area

T=250°C

hI=3214KJ/kg

T=25°C

x=0.9

Evaporator

Eco

h1=2250KJ/kg

SH

Tk

Condenser

Steam turbinex=1

pK

h0=105KJ/kg

Rankine cycle of usual process in the T-s Diagram


12% heat transfer in SHII

p=40

bar

T(°

C)

s (kJ/kg K)

T=400°C

Wet steam area

T=250°C

hI=3214KJ/kg

T=540°C

p=12

0 ba

r

hII=3455KJ/kg

T=25°C

h=3051KJ/kg

x=0.9

SH1

SH2

Evaporator

Eco

T=325°C

h1=2250KJ/kg

SH

Tk

Condenser

Steam turbinex=1

pK

h0=105KJ/kg

87.9

12.1

0

10

20

30

40

50

60

70

80

90

100

Ener

gy tr

ansf

er to

ste

am (%

)

Main boilerEco, EvaporatorSH1

Extra super heater (SH2)

120bar/540°C

Rankine cycle of the new process in the T-s Diagram


Increase of ηel.≈ 4% points

T=400°C

T=24°C

T=540°Cp=12

0 ba

r

p=40

bar

x=1

p=0.03 bar

x=0.9

hII=3455kJ/kg

hI=3051kJ/kg

h=2250kJ/kg

s (kJ/kg K)

h(k

J/kg

)

∆ht 1

20ba

r/540

°C

∆ht 4

0bar

/400

°C

ηT ≈ 0.83Steam turbine

Power generation by an axial steam turbineStandard process: 40bar/400°CExample of the new process: 120bar/540°C


800

900

1000

1100

1200

1300

1400

5 6 7 8 9 10 11 12 13 14

Regulation: T=850°C / ∆t=2s

normal combustion

new process with bypass furnace(heat transfer in super heater SH2)

λ=1.7

1.9

1.41.31.2

2.0

1.1

Adi

abat

ic c

ombu

stio

n te

mpe

ratu

re (°

C)

LHVwaste (MJ/kg)Example

LHVwaste=7.4MJ/kg

Heat transfer in the bypass super heater total excess air can be lowered (λ =1.68 1.55)

O2 dry ≈ 8.6Vol.%

O2 dry ≈ 7.5Vol.%

λ=1.5

1.8

1.6

reduced energy loss in the off gasηel. ≈ +1.5% points

Adiabatic combustion temperatures in the flue gas burnout zone of the main furnace

Tmax. refractory


Economic benefit (for the example)

MSWI with thermal capacity of 50MWOperation time per year: 8000hPrice for electricity in Germany: ≈50€/MWh

1.1 million € per yearAdditional profit:

Increase of power generation +5.5% points


p 1

TSH

K

Wet steam area

Evaporator

Eco

CondenserTC

T(°

C)

s (KJ/kg K)

Steam turbine

Super heater

p 1

TSH

K

Wet steam area

Evaporator

Eco

CondenserTC

T(°

C)

s (KJ/kg K)

Steam turbine

Super heater

p 1

p 2

TSH

K

Wet steam area

Evaporator

Eco

CondenserTC

T(°

C)

s (KJ/kg K)

Steam turbine

Super heater

p 3Intermediate steam reheating

Rankine cycle (high/medium/low pressure) like in modern power plants

ηel. >35% possible

The new process allows high steam super heating(T»500°C) avoiding chlorine induced boiler corrosion and super heater fouling

Further increase of power generation efficiency

p 1

p 2

TSH

K

Wet steam area

Evaporator

Eco

CondenserTC

T(°

C)

s (KJ/kg K)

Steam turbine

Super heater

40bar/400°C T »500°C

T »500°C T »500°C


Secondary air

Primary air

Flue gas

λ<1

λ>1

Fuel gas

Flue gas IIRecirculation

MSW+ sand

Bottom ash+ sand

Flue gas burnout zone

Cyclone

sand + coarse ash

air

λ<1

•Gas cleaning•Combustion•Super heating

ash

Application in various combustion systems

Grate furnace Fluidized bed furnace

Fuels: MSW, Biomass etc.

•Gas cleaning•Combustion•Super heating

Z1 Z2 Z3Z4

Primary air

Secondary air

MSW

Bottom ash

Fuel gas

Flue gas IIRecirculation

air

λ<1

λ>1

λ>1

λ>1

λ<1

Flue gas burnoutzone

Flue gas

ash


Summary and conclusions

• Energetic utilization of the total residual waste without pre-sorting.

• Steam can be heated up to very high temperatures at high pressures comparable to fossil fuel fired power plants avoiding super heater corrosion and fouling. This is the basis for further improvements like intermediate superheating of the steam.

• The excess air of total combustion process can be minimized resulting in reduced energy loss of the exhaust gas flow.

• The formation of pollutants particularly of NOx can be lowered significantly. As result the efforts in NOx control can be minimized or even avoided.

• All environmental aspects like low stack emissions, minimized amount of residues with good qualities allowing utilization or land filling are ensured.

• As overall optimization a very high efficiency of power generation (ηel. >35%) from a mono-fuel fired WtE plant can be realized.

Documents

A new technology for high efficient Waste-to-Energy plants€¦ · 3 H. Hunsinger - ICIPEC 2010 Institute for Technical Chemistry - ITC-TAB Today more than 70 MSWI plants Total incineration