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Praxair, Inc. - Business Confidential 1
Basics of Combustion
BASICS OF COMBUSTION
Praxair, Inc. - Business Confidential 2
Worlwide Oxygen Market and Applications
49%
25%
6%
6%
4%
2% 8%
* Most of oxygen is used for high temperature metallurgical processes and combustion applications
Primary MetalSteel
- BOF*- Blast Furnace*- EAF*- Corex*- Direct Reduction*- Reheating Furnace*
Aluminum- Melting Furnace*
Copper- Smelting Furnace*- Anode Furnace*
Chemicals/Refinery- Ethylene Oxide- Syngas*- TiO2*- Claus Sulfur*- FCC Regenerator*- Sulfuric acid recovery*
Glass/Clay/Concrete- Melting Furnace*- Cement Kiln*
Welding & Cutting*
Healthcare
Pulp & Paper- Delignification- Black Liq. Gasfication*
Others - Waste Water- Aerospace*- Coal Gasification*
Source: Salomon Smith Barney 2002
Praxair, Inc. - Business Confidential 3
Effects on Oxygen Enrichment on GeneralCombustion Characteristics
z Higher Flame Temperature is useful for welding, cutting and melting.
z Higher Flame Speedis useful for intense combustion.
z Lower Ignition Temperatureis useful for combustion of low heating value waste.
z Wider Flammability Rangeis useful for flame stability.
Praxair, Inc. - Business Confidential 4
Benefits of Oxygen Combustion
Fuel Savings
Productivity Improvement
Equipment Cost Savings Flue gas cleanup (due to lower flue gas flow rate ) Elimination of regenerators and recuperators
Reduced Emissions NOx, Particulates, CO CO2 (through energy efficiency)
Praxair, Inc. - Business Confidential 5
Air and Oxy-Fuel Combustion
COMBUSTION OF METHANE
Air-Fuel
CH4 + 2O2 + 8N2 2H2O + CO2 + 8N21.07 Nm3 of Air/Mcal
9600 scf of Air/MM Btu
Oxy-Fuel
CH4 + 2O2 2H2O + CO20.22 Nm3 of O2/Mcal
2000 scf of O2/MM Btu
cp (cal/g/K, Btu/lb/R)CO2 0.20O2 0.22N2 0.247H2O (Liq) 1.0H2O (Vap) 0.5
Lvap H2O = 546 kcal/kg (978 Btu/lb)
Praxair, Inc. - Business Confidential 6
Oxygen Combustion Significantly ReducesFlue Gas Volume
Praxair, Inc. - Business Confidential 7
Oxygen Combustion Significantly ReducesFlue Gas Volume
E
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g
y
Praxair, Inc. - Business Confidential 8
FUEL
FLUEGAS
WALLLOSS
PROCESS
Generic Energy BalanceAir-Fuel Combustion
E
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y
Praxair, Inc. - Business Confidential 9
FUEL
FLUEGAS
WALLLOSS
PROCESS
Generic Energy BalanceOxy-Fuel Combustion
E
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y
Praxair, Inc. - Business Confidential 10
Oxygen Combustion Significantly ReducesFlue Gas Volume
E
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g
y
Praxair, Inc. - Business Confidential 11
FUEL
FLUEGAS
WALLLOSS
PROCESS
Generic Energy BalanceAir-Fuel Combustion
E
n
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r
g
y
Praxair, Inc. - Business Confidential 12
FUEL
FLUEGAS
WALLLOSS
PROCESS
Generic Energy BalanceOxy-Fuel Combustion
kCHARGE > kREFRACTORY
k (W/m/K)Aluminum 200Copper 384Iron 60Steel 50Lead 35Alumina 18Mullite 6ZrO2 2SiO2 1.3
Higher emissitivy(eAIR = 0.17 vs. eOXY = 0.33)
Higher Residence TimeHigher Thermal EfficiencyE n
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y
Praxair, Inc. - Business Confidential 13
Thermal Efficiency (Net Heat Available)Air-Fuel Combustion
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
800 900 1000 1100 1200 1300 1400 1500 1600
Flue Gas Temperature (oC)
T
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E
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Air-Fuel
T
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E
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Air at 25 oC
Stoichiometric O2:Fuel Ratio
Praxair, Inc. - Business Confidential 14
Thermal Efficiency (Net Heat Available)Air-Fuel vs. Oxy-Fuel Combustion
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
800 900 1000 1100 1200 1300 1400 1500 1600
Flue Gas Temperature (oC)
T
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E
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Air-Fuel Oxy-Fuel
T
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E
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Air at 25 oC
O2 at 25 oC
Stoichiometric O2:Fuel Ratio
Praxair, Inc. - Business Confidential 15
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
800 900 1000 1100 1200 1300 1400 1500 1600
Flue Gas Temperature (oC)
T
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a
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E
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Air-Fuel Oxy-Fuel Air (400 degC) Air (1000 degC)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
800 900 1000 1100 1200 1300 1400 1500 1600
Flue Gas Temperature (oC)
T
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Air-Fuel Oxy-Fuel Air (400 degC) Air (1000 degC)
Thermal Efficiency (Net Heat Available)Air-Fuel vs. Oxy-Fuel Combustion
Air at 25 oC
O2 at 25 oC
Air at 400 oC
Air at 1000 oC
Stoichiometric O2:Fuel Ratio
Praxair, Inc. - Business Confidential 16
Potential Fuel Savings for Key Markets
0 250 500 750 1,000 1,250 1,500
Air Preheat Temperature (C)
Flue Gas Temperature (C)
272605388161093 Aluminum
Steel
Boiler
0
1020
30
40
5060
70
8090
100F
u
e
l
S
a
v
i
n
g
s
(
%
)
Glass
Fuel: Methane, 2% O2 In Flue Gas
0 250 500 750 1,000 1,250 1,500
Air Preheat Temperature (C)
Flue Gas Temperature (C)
272605388161093 Aluminum
Steel
Boiler
0
1020
30
40
5060
70
8090
100F
u
e
l
S
a
v
i
n
g
s
(
%
)
Glass
Fuel: Methane, 2% O2 In Flue Gas
Praxair, Inc. - Business Confidential 17
Adiabatic Flame Temperature for Natural Gas
Praxair, Inc. - Business Confidential 18
Adiabatic Flame Temperature for Natural Gas
Praxair, Inc. - Business Confidential 19
Principle of low NOx Aspirator Burner
OXYGEN HIGH VELOCITYLOW VOLUME
FUEL
LOW TEMPERATUREHIGH MOMENTUM
ASPIRATION OF FURNACE GASES
O2 + FURNACE GASES
LOW VELOCITYHIGH VOLUME
PRAXAIRS A BURNER
AIR LOW VELOCITYHIGH VOLUME
FUELAIR BURNER
LOW TEMPERATUREHIGH MOMENTUM
OXYGENLOW VELOCITYLOW VOLUME
FUELCONVENTIONAL OXYGEN BURNER
HIGH TEMPERATURELOW MOMENTUM
Praxair, Inc. - Business Confidential 20
Praxair A BurnerProvides Benefits of Oxygen at Low Flame Temperature
Fuel Tube
Oxygen NozzlesAnnulus Oxygen
Oxygen Jet
Oxygen to Annulus
Combustion Gases
Oxygen Envelope
Fuel Jet
Combustion Gases
Oxygen Jet
Oxygen to Nozzles
Fuel
Praxair, Inc. - Business Confidential 21
2100
2000
1900
1800
Furnace Wall Temperature (F)
Isotherms, F
Measured Flame ShapeFiring Rate = 1 MMBTU/HRA Burner - Straight Nozzles
2400
28001800
90
Furnace Length, Inches
F
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W
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,
I
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Burner
20
10
-20
-10
0 10 20 30 40 50 60 70 80
0 280024002300
2000
1950
Flame Temperature Adjustability with Oxy-Fuel
Praxair, Inc. - Business Confidential 22
2100
2000
1900
1800
Furnace Wall Temperature (F)
2150 Isotherms, F
2150
Measured Flame ShapeFiring Rate = 1 MMBTU/HRA Burner - 30 Divergent Nozzles
2100
2050
2300
2300
1580 1700
90
Furnace Length, Inches
F
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n
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W
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I
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Burner
20
10
0
-20
-10
0 10 20 30 40 50 60 70 80
Flame Temperature Adjustability with Oxy-Fuel
Praxair, Inc. - Business Confidential 23
Oxygen Combustion General Characteristics
z Higher Thermal Efficiency (Net Heat Available)
z Higher Emissivity (0.33 with oxy vs. 0.17 with air)
z Oxy-Combustion process can promote low peak flame temperature with burners properly designed and sized.
z Higher Average Bulk Flame Temperature
z Higher Combustion Products Residence Time
Praxair, Inc. - Business Confidential 24
Fuel Oil ViscosityImportance on Atomization
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