ChemCom at TKK

Mika Järvinen, Ari Kankkunen, Pasi Miikkulainen, Carl-Johan Fogelholm

Helsinki University of Technology

HELSINKI UNIVERSITY OF TECHNOLOGY Liekki-päivä, 23.1.2008 Tampere

Sub-project I: Black Liquor Spray and Droplet Properties in the Recovery

Furnace

Ari Kankkunen, Pasi MiikkulainenHelsinki University of Technology

HELSINKI UNIVERSITY OF TECHNOLOGY ChemCom Technical Fall Meeting 2007

Objective

• Spray and droplets properties in the furnace• Droplet size and other spray properties were measured in

a test chamber earlier. Are results applicable to a furnace?• Droplet size and shape were documented inside a furnace

for the first time– Are droplets spherical inside the furnace? – What is the relevant droplet size?– What is the velocity of the droplets?– What is the shape of the spray?

The test arrangement

Modifiedsplashplate

nozzle

Furnacewall

Imagingand

positioningsystems

Fast shutterspeed

cameras

SprayMeasurementpoints

2.3 m 2.3 m

Spray at varying locations, 4 l/s)above center line below

2 m

4 m

Average spray velocities at three distances fromthe nozzle

0

2

4

6

8

10

12

14

0 1 2 3 4 5

Distance to nozzle [m]

Velo

city

[m/s

]

3 l/s4 l/s

Drop size inside the furnace

0123456789

10

0 1 2 3 4 5

Distance to nozzle [m]

mm

d [m

m]

3 l/s4 l/s

Fast swelling of a droplet

50 mm

Conclusions

High quality imaging inside the furnace is possibleSpray dimensions, velocity and roughly density can be

determinedSpray particles can be detected; most droplets are lumpy, the

amount of burning particles inside the spray is normallysmall

Some droplets swell very fast and forms a balloon likegrowing surface -> ISP

Problems with high particle density and changingbackground illumination, analysis by computer is difficult

Sub-project II: ComprehensiveCFD Single Droplet Sub-model

Development

Mika JärvinenHelsinki University of Technology

HELSINKI UNIVERSITY OF TECHNOLOGY ChemCom Technical Fall Meeting 2007

Objectives of this work

Development, validation, testing and CFD implementation of a simplified droplet model (since 1999: Tekes/CODE, Academy of Finland, ChemCom)

Determine the role of single droplet sub-models in boilersimulations. Does it make any difference what kind of a single droplet model is used?

Due to computational restrictions, some phenomena can not be resolved in boiler simulations. Are there essential information for droplet conversion lost?

- 3 isothermal layers- const. Tb, Tp- only Ts(t) solved !!!!!- 8 tracked species- Na + K => M- ”fits” well into FLUENT format

H2O(l)+ DS

DS

C(s)N(s)

M2SO4(s)M2S(s)

M2CO3(s)

MCl(s)

Ts(t)

Tb= const

Tg

Tp= const

H2O(l)+ DS

DS

C(s)N(s)

M2SO4(s)M2S(s)

M2CO3(s)

MCl(s)

Ts(t)

Tb= const

Tg

Tp= const

Simplified droplet model

Figure 3. Principle of the new model

T T∞

Tb

TsTp

( )t

SmrS ∂

∂=′′

∂∂

−ρ&1

( )t

mSmrS

jjj ∂

∂=′′′+′′

∂∂

−ρ

&&1

( )ht

SqSrTShm

rS r ρλ∂∂

=⎟⎠⎞

⎜⎝⎛ +

∂∂

−′′∂∂

− &1

tT

cmThaR

TTcmTTcm

rT

SSqrT

SSq

iipi

n

j

n

kijjkk

iiipiiiipi

ir

ir

S R

∂∂

=−

−−−−

−⎟⎠

⎞⎜⎝

⎛∂∂

−−⎟⎠

⎞⎜⎝

⎛∂∂

−

∑∑= =

+++−−−

+−

.1 1

.

1½.½1½.½

½½

)(

)()0,max()()0,max( &&

λλ

CV-method

SOURCE TERMS

H2O(l) → H2O R.0Dry solids → C(s) + Volat. + Inorg. R.1C(s) + 0.5 O2 → CO R.2 [14]C(s) + H2O → CO + H2 R.3 [15]C(s) + CO2 → 2 CO R.4 [16]M2SO4(s) + 2 C(s) → M2S(s) + 2 CO2 R.5 [17]M2S(s) + 2 O2 → M2SO4(s) R.6 [14]M2CO3(s) + 2 C(s) → 2 M + 3 CO R.7 [18]

VALIDATION

C-release rate for 2.5 mm particle burned in 3% O2, 900 °C, experiments from [12]

0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25Time, s

Car

bon

rele

ase

rate

, mg/

sDetailed Simplified

Swelling for 2.5 mm particle burned in 3% O2, 900 °C, experiments from [12]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25Time, s

Sw

ellin

g, d

/d0

Detailed Simplified

Application to other fuels• CFD sub-model developed is based on a general “conservation

equation approach”• Therefore, application to other fuels (wood, biomass, coal, …) is

possible, model is not fuel specific.• Primary conservation equation system “The Solver” remains the

same, what needs to be updated is:– Fuel composition, species– Reaction stoichiometry, kinetic parameters– Particle shape, sphere as the first assumption, we have also

experience from other shapes with the detailed model (ICRC 2004, Charleston)

– Swelling parameters– Boundary conditions (in-flight, grate, dense suspension, …)

• this work is already started (ÅA, Biomass) first results published at AJFR at Havaji