An experimental approach to the kinetics of the combustion ... 4_C/4... · Effect of gas composition for Ger1 and Ger2 50) air 21/79 30/70 40/60 50/50 Ger1 30 40 o n time (in s 40

An experimental approach to the kinetics of the combustion

in O2/CO2-atmospheres

Stephanie TappeHans Joachim Krautz

Chair of Power Plant TechnologyB d b U i it f T h l C ttb

1st Oxyfuel Combustion Conference Cottbus, 7th-11th September 20091

Brandenburg University of Technology CottbusGermany

Outline

1 Motivation

2 ALVA 20 and experimental set up2 ALVA 20 and experimental set up

3 Experimental results and discussion

4 Summary and outlooky


Outline

1 Motivation2 ALVA 20 and experimental set up2 ALVA 20 and experimental set up




Motivation

Combustion procedure

• Preheating• DryingDrying• Devolatilization, ignition and combustion of volatile matters

(homogeneous gas reaction)• Ignition and combustion of charg

(heterogeneous gas-solid reaction)

Oxyfuel-atmosphere:Oxyfuel atmosphere:• Increased CO2 partial

pressure• Increased H2O partial


Increased H2O partial pressure

C b ti f l til tt

Effects of increased CO2-concentrations

Combustion of volatile matters Heat capacity

heat transfer ignition

Combustion of char

Heat capacityflame temperature reaction rate

CO2-concentration CO2 concentrationdiffusion rateschemical reaction mechanisms


Focus of work

Effect of increased CO2-concentrations in the burning behaviour

Applying ALVA 20• Registration of the whole combustion sequence• Close-to-reality-conditions - high heating rates

- fluid dynamics

Applying ALVA 20

y- particle interactions


Outline

1 Motivation

2 ALVA 20 and experimental set up2 ALVA 20 and experimental set up3 Experimental results and discussion



20 kWth atmospheric laboratory test facility - ALVA 20


ALVA 20


Temperature range

Experimental set up

Temperature range 800 – 1000°C

Particle size 1.25 - 2.00 mm

FuelGer1, Ger2Pol, US-Bl

Gas compositionGas composition air, O2/CO2 with 5-50 vol.-% O2


Data analysis

I j ti E d f

n vo

l.-%

) Injection of sample

End ofexperiment

trat

ion

(in

Char combustion

2-co

ncen

t

Combustion ofvolatile matters

0 10 20 30 40Ti (i )

O2


Time (in s)

Outline

1 Motivation


3 Experimental results and discussion4 Summary and outlooky


Combustion sequences for different O2-concentrations60

%) 05/95 10/90 21/79 30/70 40/60 50/50

50

(in v

ol.-%

05/95 10/90 21/79 30/70 40/60 50/50

Ger1

30

40

ntra

tion

20

en c

once

n

0

10

Oxy

ge


0 10 20 30 40 50Time (in s)

Combustion sequences for different gas compositions

Ger1

1000°C

800°C

Pol

1000°C

0 10 20 30 40 50

air air21/79 21/79

Pol

800°C

0 10 20 30 40 50Time (in s)

air air21/79 O2/CO2 21/79 O2/CO2


0 10 20 30 40 50Time (in s)

Data interpretation – Approach I

25

20

25

n vo

l.-%

)

tv

10

15

trat

ion

(in

5

10

-con

cent

00 10 20 30 40 50

Time (in s)

O2


Time (in s)

Effect of gas composition for Ger1 and Ger250

)

air 21/79 30/70 40/60 50/50 Ger1

30

40

on ti

me

(in

s)40

50

n s)

air 21/79 30/70 Ger210

20

Com

bust

io

20

30

stio

n tim

e (i

n

01050 1100 1150 1200 1250 1300 1350

Temperature (in K)

0

10Com

bu


01050 1100 1150 1200 1250 1300 1350

Temperature (in K)

Effect of gas composition for Pol, US-Bl50

air 21/79 30/70 40/60 50/50 Pol

30

40

on ti

me

(in

s)

air 21/79 30/70 40/60 50/50 Pol

50 10

20

Com

bust

io

30

40

on ti

me

(in

s) 01050 1100 1150 1200 1250 1300 1350

Temperature (in K)

0

10

20

Com

bust

i

air 21/79 30/70 US-Bl


01050 1100 1150 1200 1250 1300 1350

Temperature (in K)

Determination of keff,char 25 2

kX )1l (20

n vo

l.-%

)

0tkX eff )1ln(

10

15

trat

ion

(in

4

-2

ln (1

-X)

5

10

2-co

ncen

t

-6

-4 l

00 5 10 15 20 25 30

O2

-8


0 5 10 15 20 25 30

time (in s)

Data interpretation –Approach II

20

25

vol.-

%)

15

atio

n (in

v

Char combustion

5

10

conc

entr

a

Combustion of

volatile

0

5

0 10 20 30 40 50

O2-

c volatile matters


0 10 20 30 40 50Time (in s)


25

20

25

vol.%

)

fa fdfe

15

ratio

n (in

fb fc

5

10

2 con

cent

r

00 10 20 30 40 50

O2


0 10 20 30 40 50Time (in s)

Outline

1 Motivation





Summary and Outlook

T t• T tv

• c(O2) tv

• Combustion sequence changes:Trend: tv (air) > tv (O2/CO2) for c(O2)const but but f (T, fuel)

Next Steps:

• Considering specific surface area

• Determination of kinetics applying approach II (VM, char)


Acknowledgement

The research work was financed by the DFG (Deutsche Forschungsgesellschaft).

It is sponsored at the title: „Charakterisierung des Abbrandverhaltens von Braunkohlen in O2/CO2-Atmosphären“ (Kr 1855/9-1).


Thank you yfor your attention!

Contact: Stephanie Tappetappe@tu cottbus de


[email protected]

Fuel composition

Proximate Analysis Ultimate Analysis

Moisture Ash Volatiles C-fix Heating value C H N S O value

Coal (wt.-%) (wt.-%) (wt.-%) (wt.-%) (MJ/kg) (wt.-%) (wt.-%) (wt.-%) (wt.-%) (wt.-%) Ger1 18.03 5.25 45.40 31.32 20.41 52.91 7.34 0.52 0.72 15.23 lig Ger2 8.81 13.32 50.94 26.93 23.29 56.40 12.53 0.48 3.30 5.16 Pol 7.00 6.92 29.89 56.19 27.83 70.65 6.96 1.13 0.41 6.93 US Bl 1 73 12 39 30 66 55 22 29 89 72 26 8 17 1 39 0 89 3 17bit US-Bl 1.73 12.39 30.66 55.22 29.89 72.26 8.17 1.39 0.89 3.17bit SA-Bl 8.48 15.33 22.12 54.06 24.34 65.16 3.45 1.55 0.47 14.04


dn

Determination of keff,char

2

2Oeff

O nkdt

dnr

ktnO2)(

l

Reaction rate

)(

tkn eff

complO

O 2

2ln

tn )(

222)( OcomplOO nntn

complO

O

ntn

X,2

2)(

Conversion of O2

tkX eff )1ln(


combustion process volatile matters Integration


combustion process volatile matters

char

Integration

Differentation

Combustion of volatile matters2

2)( OvolO nk

dtdn

tr t

d

t

tOOcomplO dttccVn

0

.

, )()0(222

dtdc

tr O2)( Char combustion

tkc

charO 2ln


tkc char

O 0,2

Effect of gas composition for SA-Bl

50

40

50

in s

)

30

on ti

me

(i

10

20

Com

bust

io

01050 1100 1150 1200 1250 1300 1350

C

air 21.79 30.70 SA-Bl


Temperature (in K)

Documents

An experimental approach to the kinetics of the combustion ... 4_C/4... · Effect of gas composition for Ger1 and Ger2 50) air 21/79 30/70 40/60 50/50 Ger1 30 40 o n time (in s 40