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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
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
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]
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