Simulation of Burden distribution in an Ironmaking
blast furnace
Tamoghna Mitra
Thermal & Flow Engineering Laboratory,
Åbo Akademi University.
SIMP program, Showcase 3
Steel industry
Raw materials DRI ironmaking
Blast Furnace
ironmaking
Iron oxide
Iron (5% C)
Steelmaking
70 %*
Steel (0.05 -1% C)
Downstream
* worldsteel.org
Semi-finished products
Blast Furnace Ironmaking
2C+O2→2CO
Fe2O3+CO→Fe+CO2
Iron ore (Fe2O3),
Coke, flux
CO, CO2
Oxygen
Hot metal, Slag
Importance of BF research
1.255 t CO2/t steel a
c
World per capita energy consumption c
Direct CO2 emissions in industry by sector, 2007 b
69 % of all steel
mill emissions!!! b
a.
b.
0.569 t coal/t steel
a
c.
d.
Birat, “Steel and CO2 – the ULCOS Program, CCS and Mineral Carbonation using
Steelmaking Slag”
International Energy Agency, “Energy, Technology, Perspectives: Scenarios &
strategies to 2050”, 2010.
Organisation for Economic Co-operation and Development, “Steelmaking raw
materials: Market and policy developments”, 2012
Gail Tverberg, “Can We Expect The Economy To Keep Growing?”, 2012
Burden distribution: Raw material charging
Layered structure
– slowly descending burden
–
rising reducing gas from below
Rings of ore and coke
Charging program– (material, amounts,
position) effects the radial distribution of
ore and coke
Effect on gas distribution
–
–
Coke: High porosity
Ore: Low porosity
Effect on thermal conditions
–
–
Coke: Low density
Ore: High density
Effect on the formation of deadman
(stagnant region of coke at the bottom)
and the coke slits (Regions of high
porosity coke in the less permeable ore
regions of cohesive zone
AIM: Understand the effects of different
burden distribution programs on the gas
distribution and furnace performance
Burden distribution simulation
Multi-physics models
Mathematical models
–
–
–
–
Simple
Fast
Fairly accurate
Good for designing charging
programs
– Evaluate overall conditions
– We use in-house code
(BURDEN)
Experimentation using
scaled models
–
–
–
–
Slow
Expensive
Scalability of results
Limited insight of the layer
structure
– Good for validation
– We use 1:10 scaled
experimental setup
– Complicated: Particle-particle
and particle-gas interactions
– Slow
– Very accurate
– Good for developing
understanding
– Evaluate local phenomena
– We use Discrete Element
Modelling.
BURDEN (Burden distribution program)
Burden distribution effects
(Results from BURDEN)
2
(m)
2
dinate (m)
200
0 -2
-4
-2 0
0 2
2
-2
0
2
RadialRadial
coordinate
(m) (m)
coordinate
-6
0.5
1
4
600
-6
-8 5 00.5
-8
-4-2
-2 0
0 2
2
4
400
coordinate
RadialRadial
coordinate
(m) (m)
-8
-2
0
2
0
200
4 10 Radial
-4 coordinate
-2
0 (m) 2
4
-2 0 2
Radial coordinate (m)
Radial coordinate (m)
0.5
0
-2
10
-4
0
2
-2
0
2
-2
0
2
coordinate
(m)
Radial coordinate
(m)
Radial
coordinate (m)
10
4
800 -6
0.5
400
Radial
Height (m)
Ore/(Ore+Coke)
Ore/(Ore+Coke)
0
-8
600
1
5
0.5
-4
0
-2
0
2
Radial coordinate (m)
1
200
4
4
800
0.5
600
0.5
05
-2
0
2
-4
-2
0
2
4
400
Radial coordinate
(m)
Radial coordinate
(m)
0
10-4
-2
0
2
-2Radial
0 coordinate
2
(m)
Radial coordinate (m)
200
4
800
800
1
600
600
5
5
400
400
0
-410
-2
0
2
-2
0
2
Radial coordinate (m)
10
-2 coordinate
0 2 (m)
Radial
1
Radial coordinate (m)
0.5
0
0
0 5
-45
Height (m)
0.5
Ore/(Ore+Coke)
Height (m)
Ore/(Ore+Coke)
10
-6
400
-8 Radial
1 0 coordinate (m)
4
-2
02
2
-2-4
0
Radial coordinate
Radial coordinate
(m) (m)
Height (m)
Height Height
(m) (m)
2
(m)
600
Height Ore/(Ore+Coke)
(m)
Ore/(Ore+Coke)
-8
-6
2
2
dinate
(m) (m)
Height (m)
Ore/(Ore+Coke)
Ore/(Ore+Coke)
Height (m)
Height
(m)(m)
Height
2
(m)
-6
1
50.5
800
1
Ore/(Ore+Coke)
Height
Height(m)
(m)
800
1
0
0
200
4
200
1
R
800
800
600
600
-2
0
2
Radial coordinate (m)
10
-2 0 2
10
-2
0 2 (m)
Radial coordinate
Radial coordinate (m)
4
400
400
200
200
Gas temperature (deg C)
Height (m)
0
Ore/(Ore+Coke)
Height
(m)
Height
(m)
0
1
R
Discrete Element Modeling
Originally introduced by Cundall and
Strack (1979)
Lagrangian method
Similar to Molecular dynamics
Explicit calculations
Solid particles undergo translation
and rotation
Satisfy Newton’s second law
– Spring and dashpot model
Soft sphere model
30.11.2015
Åbo Akademi University | Domkyrkotorget 3 | 20500
Åbo | Finland
9
Case 1: Mixed layer formation
Mixed layers
Regions of low permeability of
gases
Due to difference in particle sizes
– Coke ~ 50 mm diameter
– Pellet ~ 12 mm diameter
~4x
Small particles occupy the space
in-between the larger ones.
Irregular shape of the coke
particles increases the effect
Especially important as the coke
rate is decreases and injection
increases because of thinner
layers.
This needs to be accounted for
during gas flow calculations
Ore
layer
Mixed
layer
Coke
layer
DEM simulation
Simulation for 1:10 scale experimental setup
Voidages
Mean layer thickness
(cm)
Layers
Mixed
layer
Mean voidage
Simulatio
n
Experiment
Simulation
Pellet
4.54
4.58
0.509
Center
coke
-
-
-
Small coke
3.15
1.83
0.505
Large coke
1.97
2.62
0.458
Coke
(overall)
4.43
4.45
0.474
Pellet &
Small coke
1.11
-
0.445
Large coke
& Small
coke
0.68
-
0.439
Case 2: Coke collapse effect
Radar
Coke collapse
Influences the radial variation
of volumetric ore-to-coke
fractions
Profile measurements using a
radar may be misleading
Difficult to quantify without
multi-physics simulation
Coke dump
~4x
Measured height
– Ore ~ 2200 kg/m3, bulk density
– Coke ~ 500 kg/m3, bulk density
Ore dump
Radial distance
Actual height
Deformation of the coke layer
when ore layer is charged on top
of it, especially at higher angles.
Mainly due to the difference in
densities of the two kinds of
charged materials
Radial distance
Coke collapse experiment and DEM
simulation
*2 million particles
Slope stability using “Method of Slices”
Use “Method of slices” to quantify the
coke collapse during charging.
Thereafter improve the mathematical
model to take into account this issue,
for more realistic results.
Calculate the factor of safety for a
slope under loading conditions.
Change the slope until a safe factor is
reached
Conclusions and Future work
DEM may be used to have a greater insight on the
burden charging operation in a blast furnace.
Mixed layer formation has been modelled and
quantified for small scale experimental setup, in
future the same study would be done for a full scale
simulation.
Coke collapse has been observed using both
simulation and experiment. In future, it would be
quantified using the “Method of slices”.
Results from the DEM will be used to modify the
simplified burden distribution model. (BURDEN)