HELSINKI UNIVERSITY OF TECHNOLOGY
Liekki-päivä, 23.1.2008 Tampere
ChemCom at TKK
Mika Järvinen, Ari Kankkunen,
Pasi Miikkulainen, Carl-Johan Fogelholm
Helsinki University of Technology
HELSINKI UNIVERSITY OF TECHNOLOGY
ChemCom Technical Fall Meeting 2007
Sub-project I: Black Liquor Spray and
Droplet Properties in the Recovery
Furnace
Ari Kankkunen, Pasi Miikkulainen
Helsinki University of Technology
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
Spray
Measurement
points
Furnace
wall
Modified
splashplate
nozzle
Imaging
and
positioning
systems
2.3 m
2.3 m
Fast shutter
speed
cameras
Spray at varying locations, 4 l/s)
above
2m
4m
center line
below
Average spray velocities at three distances from
the nozzle
14
Velocity [m/s]
12
10
8
3 l/s
4 l/s
6
4
2
0
0
1
2
3
Distance to nozzle [m]
4
5
mmd [mm]
Drop size inside the furnace
10
9
8
7
6
5
4
3
2
1
0
3 l/s
4 l/s
0
1
2
3
Distance to nozzle [m]
4
5
Fast swelling of a droplet
50 mm
Conclusions
High quality imaging inside the furnace is possible
Spray dimensions, velocity and roughly density can be
determined
Spray particles can be detected; most droplets are lumpy, the
amount of burning particles inside the spray is normally
small
Some droplets swell very fast and forms a balloon like
growing surface -> ISP
Problems with high particle density and changing
background illumination, analysis by computer is difficult
HELSINKI UNIVERSITY OF TECHNOLOGY
ChemCom Technical Fall Meeting 2007
Sub-project II: Comprehensive
CFD Single Droplet Sub-model
Development
Mika Järvinen
Helsinki University of Technology
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 boiler
simulations. 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?
Simplified droplet model
Tg
Ts(t)
Tp= const
Tb= const
H2O(l)
C(s)
+ DS
N(s)
MCl(s)
DS
M2S(s)
M2SO4(s)
M2CO3(s)
- 3 isothermal layers
- const. Tb, Tp
- only Ts(t) solved !!!!!
- 8 tracked species
- Na + K => M
- ”fits” well into FLUENT
format
∂ρ
1 ∂ &
′
′
(m S ) =
−
S ∂r
∂t
∂ρj
1 ∂ &
&
m ′′j S + m ′j′′ =
−
S ∂r
∂t
(
−
)
1 ∂ ⎛&
∂T
⎞ ∂
S + q r S ⎟ = (ρ h )
⎜ m′′ h S − λ
∂r
S ∂r ⎝
⎠ ∂t
T
T∞
Ts
Tp
Tb
CV-method
∂T ⎞
∂T ⎞
⎛
⎛
−
− ⎜ qr S − λS
⎟
⎜ q r S − λS
⎟
∂
r
r
∂
⎠i +½
⎝
⎠i −½ ⎝
max(m& i − ½ c p.i − ½ , 0) (Ti − Ti −1 ) − max(− m& i + ½ c p.i + ½ , 0) (Ti − Ti +1 )
−
nS
nR
∑∑ R
k
j =1 k =1
ak . j h j (Ti ) = mi c p.i
∂Ti
∂t
Figure 3. Principle of the new
model
SOURCE TERMS
H2O(l) → H2O
Dry solids → C(s) + Volat. + Inorg.
C(s) + 0.5 O2 → CO
C(s) + H2O → CO + H2
C(s) + CO2 → 2 CO
M2SO4(s) + 2 C(s) → M2S(s) + 2 CO2
M2S(s) + 2 O2 → M2SO4(s)
M2CO3(s) + 2 C(s) → 2 M + 3 CO
R.0
R.1
R.2
R.3
R.4
R.5
R.6
R.7
[14]
[15]
[16]
[17]
[14]
[18]
VALIDATION
Carbon release rate, mg/s
0.6
Simplified
0.5
Detailed
0.4
C-release rate for 2.5
mm particle burned in
3% O2, 900 °C,
experiments from [12]
0.3
0.2
0.1
0
0
5
10
15
Time, s
20
25
3.5
Detailed
Simplified
Swelling, d/d0
3.0
2.5
2.0
1.5
Swelling for 2.5 mm
particle burned in
3% O2, 900 °C,
experiments from
[12]
1.0
0.5
0.0
0
5
10
15
Time, s
20
25
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