Post on 09-Jul-2020
Sebastian März (Otto Junker, Lammersdorf)Prof. Dr. Herbert Pfeifer (RWTH Aachen University, Department
of Industrial Furnaces and Heat Engineering)
„Modern Furnaces for theAluminium Industry “
Thursday, December 11st 2014
raw
material
charging
cold rolling
pusher-type
furnace
chamber furnace
artificial ageing
strip miller or
saw and slab
miller
hot rolling
roller hearth furnace solution
heat treatment / quenching
melting furnace
heat treatment of
plate customer
foil rolling mill
continuous strip annealing line
chamber furnace
or
pit-type furnace
slitting or cutting to length separating cutting
chamber furnace / foil coil annealing
processing
customer
stretching
pouring furnace
homogenizing in
pusher-type or
pit-type furnace
Process routes for the production of aluminium flat products basedon secondary raw materials
Convective heat transfer to rolling slabs, (a) impingement flow, (b) gap flow
Flow principles in reheating furnaces for Al slabs, (a) gap flow, (b) mass flow
Furnaces for the heat treatment of Al are dominated by convective heat transfer
Round and flat nozzle fields
Single nozzle
radiant tubes
burnersfan
furnace cover
Pit furnaceBurnerFans
Al-Pit furnace
burners
fans
burners
nozzlesystemmain
flow
pusher-type furnace
slabs
Al-pusher type furnace
Direct gas heated pusher-type furnace for pre-heating and homogenisation of Al-slabs
down ender furnace up ender
Energy and material flows for the determination of the total energy input
Characteristic mass flows of combustion
Energy balances and system boundaries for an industrial furnace
with air preheating
Combustion efficiency
Advantage and characteristics of flameless oxidation
– Development and enhancement of fuel fired burners– main goal: increase of efficiency– use of high off-gas enthalpy for air preheating– challenge: Reduction of high NOx-emission
– FLOX® - Combustionreaction without flame– high inlet velocity (> flame velocity)– recirculation of off-gas– increase of reacting volume– homogenization of temperature in reaction zone– no temperature maxima as in flame-front– significant dedrease of NOx-emission
17
18flame operation mode FLOX®- operation
� flame operation mode for heat-up process
� (blue) stoiciometric gas flame
� power: 8 kW
19
NOx-Reduction in FLOX®- operation mode (Treactor = 840 °C)
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
2,0
0
20
40
60
80
100
120
140
160
180
200
00:00 05:00 10:00 15:00 20:00 25:00
Air
rat
io
con
cen
trat
ion
in p
pm
time in minutes
NOx
LuftzahlAir ratio
NOx
Fans4 x 90 kW
Radiant tubes8 x 200 kW
Inner casing
Nozzle field
Sleeve
Coil
4 Zones
Energy Momentum Turbulence
Simulation of fluid flow
Simulation of structure
Thermal expansion Stress / Strain
1-Way Coupling: small deformations fluid flow structure
Fluid-Structure-Interaction (FSI) in the field of i ndustrial furnace engineering:
Total heat flux and temperature distributioninsulation
Stresses on the radiant heating tube (1)
Intersection between insulation and furnace chamber
high temperature gradient (approx. 100 K)
high stresses
Stresses on the radiant heating tube (2)
different temperatures between thearms of the radiant tube
∆T ≈ 20…40 K
∆T betweenarms ∆T internal side
Stress and strain as a function of circumference
680
690
700
710
720
730
740
0 1 2 3 4
0.0125
0.0126
0.0127
0.0128
0.0129
0.0130
0.0131
0.0132
tem
pera
ture
in °C
position of circumference
stra
in in
mm
/mm
strain ε
temperature
0
20
40
60
80
100
0.010
0.011
0.012
0.013
0.014
0.015
0 1 2 3 4
stre
ss in
MP
a
stra
in in
mm
/mm
position of circumference
strain εstrain ε_theor.stress
Contribution of stresses on the radiant heating tub e
0 20 40 60 80 100
∆T arms
∆T internal side
∆T wall thickness
gravitation
maximum stresses in MPa
Fans4 x 90 kW
Radiant tubes8 x 200 kW
Inner casing
Nozzle field
Sleeve
Coil
4 Zones
Temperatur in K
Fans4 x 90 kW
Radiant tubes8 x 200 kW
Inner casing
Nozzle field
Sleeve
Coil
4 Zones
Volume flow measurement
0
1000
2000
3000
4000
5000
6000
0 1 2 3 4 5 6 7 8 9
Tota
ldru
cker
höhu
ng
∆∆ ∆∆ptin
Pa
Volumenstrom V ̇ in m 3/s
nV = 2540 min-1
nV = 1600 min-1 Soll-Kennlinie
eigene Messung
30Ziel dieses Projektes: kontinuierliche Volumenstromerfassung
als Standardmessung in Wärmebehandlungsöfen
Deutliche Abweichungen zwischen Herstellerangaben (Normprüfstand) und Ofen/Versuchsstand
∅1
∅1 15
RM
P
pref
pt
pref
pt
Die Messpositionen des Messkreuzes wurden auf dem
Radius RMP = 0,74 · RME eingebracht.Messkreuz
31
&VV
32
ϕ in °
uED in m/s0
15
30
45
6075 90 105
120
135
150
165
180
195
210
225
240255270285
300
315
330
345
0 0
0
0
10 10
10
10
20 20
20
20
30 30
30
30
φφφφ in °
Strömungsgeschwindigkeit in der Einlaufdüse
als Funktion des Azimuts ϕ(Polarkoordinaten, z = 80, r = 190 mm)
φ ReED · 10-5 nV in min-1
���� 1 0,274 9,38 1600
���� 2 0,188 6,44 1600
3 0,075 2,65 1600
���� 4 0,054 1,85 1600
���� 5 0,188 9,38 2330
Laufraddurchmesser: D2 = 650 mm
33
0,075
kMK = const = 0,76
ϕ = ⋅&
VV
V
Vk
n
RMP = 0,74 · RME
34
36
Casting up to 700 °C
PreHeat / Homogenizationup to 550 °C
Stress Relief up to 550°C
Homogenizationup to 550 °C
Strip Solutionizingup to 550°C
Plate Solutionizingup to 550 °C
Aging up to 200 °C
PreHeat / Homogenizationup to 550 °C
Casting up to 700 °C
Interm. Anneal upto 550 °C
Final. Anneal up to550 °C
Final. Anneal up to550 °C
Technology Today
38
• Coil Annealing Furnaces for Intermediate or Temper Annealing of rolledaluminium coils
• Discontinous process:
• Compiling the batch
• Feeding the Furnace, Start of Heat Treatment
• Heat Treatment
• End of Heat Treatment – Remove the Batch
Stand der Technik - Prozessführung
39
Heat Treatment Process
• …either according to pre determined receipe (Temperature/Time/Fanspeed)
• Or according to measured metal temperature
40
Mathematical model for increase of energy efficiency
•Energy demand and CO 2 emission of coil annealing furnaces
• Reference: aluminium, 20-420°C, energy demand: 185 kWhth/t and 28 kWhel/t, respectively
• At an annual output of 1.8 million tonnes of flat products, at • least 100,000 tonnes of CO2 are released for intermediate • and final annealing purposes in Germany alone.
• The need to purchase CO2 emission rights is to be anticipated as of 2013
Reason enough to start examining the use of saving potentials as early as today!
41
An Aluminium Coil ....
© ELVAL
...looks like a big solid block
A microscopical view shows...
42
Heat up physics for strip coils
That a coil consists ofhundred layers ofAluminium strip
and hundreds of layersof layers of oil and air
which have an insulatingeffect, so that only
90 - 95 % of heatinput takes placevia the face ends
5 - 10 % of heat input takesplace via the circum-
ference
43
Heat up physics for strip coils
High convection heating
from the face ends is more efficient
than
mass flow around the circumference
44
Mathematical model for increase of energy efficiency
•Concept of mathematical modelling
Production planning• puts together most suitable charge lots from stock in “offline” mode
Process management• computes metal temperatures “online” and controls influencing process parameters
Interfacing
• optimizes production planning by introducingempirical process management data
Architektur
PDMLagerbestand Bandbunde
Charge SOLL
(Beladung, Rezept)
energie- oder zeitoptimierte Chargen
Charge IST
(Zeiten, Temperaturen)
Modellrechner
“offline“Modellrechner
“online“Empirische Daten
Prozessparameter SOLL
Prozessparameter IST
MMI
Visualisierung
SPSBedienung
Mathematisches Modell: e) Ergebnisse
46
-2,50%
-1,50%
-0,50%
0,50%
1,50%
2,50%
Δ (gemessene Temperatur - gerechnete Temperatur)/Materialsollwert
an den Orten K(x = b/2 ; y = 0,9 s) und K(x = 0,1 b ; y = 0,1s )
y
x
b
s
Über n=50 Chargen wurde eine Genauigkeit von besser als 1% der Zieltemperatur reproduzierbar erreicht.
47
Mathematical model for increase of energy efficiency
-5
25
55
85
115
145
175
205
235
265
295
325
355
385
0 125 250 375 500 625 750 875 1000 1125 1250
heating time in [min]
tem
pera
ture
in [°
C]
MeasCoil 1
MeasCoil 2
MeasCoil 3
GasOutlet 1
GasOutlet 2
GasOutlet 3
GasInlet 1
GasInlet 2
GasInlet 3
DevCalcCoil 3
•Operating experience:
In foil annealing, the mathematical model developed by OTTO JUNKER equalizes a 50K temperature differenc e to ± 3 K.
48
Mathematical model for increase of energy efficiency
0
250
500
750
1000
1250
1500
1750
2000
2250
2500
2750
3000
3250
0 30 60 90 120 150
increase of average entry temperature in K
carb
on d
ioxi
de s
avin
g in
mt/y
r
20000 mt/yr
30000 mt/yr
50000 mt/yr
80000 mt/yr
120000 mt/yr
170000 mt/yr
230000 mt/yr
•Estimate of potential CO 2 savings•(⅔ from fuel savings, ⅓ from reduced electrical power demand)
49
� Possible Materials � 2xxxAl-Cu
� 6xxxAl-Mg-Si
� 7xxxAl-Zn-Mg
Hig
he
r Te
mp
era
ture
Larger % Alloying Element
50
� Complete Cycle (3 steps) � Heating
� Quenching
� Aging
Hig
he
r Te
mp
era
ture
Time
51
� Complete Cycle (3 steps) � Heating
� Quenching
� Aging
Hig
he
r Te
mp
era
ture
Time
52
� Complete Cycle (3 steps) � Heating
� Quenching
� Aging
Hig
he
r Te
mp
era
ture
Time
53
� Complete Cycle (3 steps) � Heating
� Quenching
� Aging
Hig
he
r Te
mp
era
ture
Time
54
� How to prevent alloying element from segregation?H
igh
er
Tem
pe
ratu
re
Time
55
� How to prevent alloying element from segregation?
…… being fast enough
Hig
he
r Te
mp
era
ture
Time
56
� Speed matters
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
Metal Temperature
57
� Speed matters
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
Slow Cooling
58
� Speed matters
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
Fast Cooling
Slow Cooling
59
� Speed matters – as fast as necessary……….
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
Avoid that line to prevent segregation
60
� Speed matters – as fast as necessary - but as slow as possib le
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
Avoid that line to prevent segregation
61
� Different Alloys – Different Requirements
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
7075
62
� Different Alloys – Different Requirements
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
2017
63
� Different Alloys – Different Requirements
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
2017
64
� Different Alloys – Different Requirements
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
6061
65
� Different Alloys – Different Requirements
0
100
200
300
400
500
600
1 10 100 1000
Hig
he
r Te
mp
era
ture
Time
6063
66
� Strip Flotation Line � Min Gauge 0.3 mm
� Max Gauge 4 mm
� Min cooling rate: ~ 30 K/s
� Max cooling rate: > 300 K/s
67
� Alpha � Alpha ( α ) = Heat Transfer Coefficient
� α ~ v 0,7 [W/m²K]
� Determines how much heat is transfered per each m² of (contact) surface and temperature difference (Medium to metal)
68
� The higher the alpha value – the higher the cooling rateFa
ste
rC
oo
lin
g(K
/s)
Higher Alpha (W/m²K)
4 mm
� The thicker the strip, the lower the cooling rate (with gi ven alpha value)
69
4 mm
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
1.5 mm
70
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.3 mm
71
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.5 mm0.3 mm
72
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.5 mm0.3 mm 1 mm
73
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.5 mm0.3 mm 1 mm 2 mm
74
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.5 mm0.3 mm 1 mm 2 mm
2.5 mm
75
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.5 mm0.3 mm 1 mm 2 mm
2.5 mm
3 mm
76
Fast
er
Co
oli
ng
(K/s
)
Higher Alpha (W/m²K)
4 mm
1.5 mm0.5 mm0.3 mm 1 mm 2 mm
2.5 mm
3 mm
77
Fast
er
Co
oli
ng
(K/s
)
Thicker Strip (mm)
α 1.800 W/m²K
78
� Strip Flotation Line � Min Gauge 0.3 mm
� Max Gauge 4 mm
� Min cooling rate: ~ 30 K/s
� Max cooling rate: > 300 K/s
79
Fast
er
Co
oli
ng
(K/s
)
Thicker Strip (mm)
α 5.800 W/m²K
80
Fast
er
Co
oli
ng
(K/s
)
Thicker Strip (mm)
α 1.800 W/m²K
� Water Injected into Air = Mist Cooling
α ~ 200 – 1600 W/m²K
� Water Coolingα ~ 5.800 – 1.800 W/m²K
81
� Air Coolingα ~ 40 – 180 W/m²K
82
Fast
er
Co
oli
ng
(K/s
)
Thicker Strip (mm)
83
� Otto Junker Mist Quench
� Water Injected into Air = Mist Cooling
α ~ 200 – 1600 W/m²K
� Water Coolingα ~ 5.800 – 1800 W/m²K
84
� Air Coolingα ~ 40 – 180 W/m²K
85
� Water Injected into Air Stream
86
� α function of air speed
� α function of water density
87
� α function of air speed
� α function of water density
Hig
he
r A
lph
a V
alu
e (
W/m
²/K
)
88
Fast
er
Co
oli
ng
(K/s
)
Thicker Strip (mm)
89
Fast
er
Co
oli
ng
(K/s
)
Thicker Strip (mm)
Sebastian März (Otto Junker, Lammersdorf)Prof. Dr. Herbert Pfeifer (RWTH Aachen University, Department
of Industrial Furnaces and Heat Engineering)
„Modern Furnaces for theAluminium Industry “
Thursday, December 11st 2014