NAWTEC Conference – May 24-26, 2005, Orlando, FL
Thermo-Gravimetric Analysis (TGA) of Combustion and Gasification of
Styrene-Butadiene Copolymer (SBR)
Marco J. CastaldiDepartment of Earth & Environmental EngineeringHenry Krumb School of Mines, Columbia University
May 24, 2005
NAWTEC Conference – May 24-26, 2005, Orlando, FL
PresentationIntroduction
Experimental Setup
ResultsExperimental
Modeling
Conclusions
Future Work
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Introduction
Approximately 270 million tires disposed in U.S.Tires do not biodegradeReprocessing is very energy intensive because of strength and makeupMakeup (rubber and inorganic content) are well suited for energy production and material recovery
NAWTEC Conference – May 24-26, 2005, Orlando, FL
ObjectivesUnderstand the thermal decomposition process of tires under various conditions
Various atmospheresParticle size (mass burn vs other)Primary reaction mechanisms
Determine/develop higher efficiency, lower emission firing techniques
Exhaust gas recirculationPlacement of fuel and air injectionEnhancement techniques
Conduct realistic simulations for technology evaluation and application development
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Experimental SetupTire Composition
Natural RubberPoly-isoprenesCarbon BlackSulfurInerts and metals
Major synthetic rubbersStyrene Butadiene Rubber (SBR)Styrene rubber (SR)Butadiene Rubber (BR)
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Experimental Setup
N2 O2 H2
RMRMRM
80ml/min
20ml/min
Heated tubing (120oC)
Micro-GC
Calibrated Rotometers
Certified gases (pure and mixtures)
Const. Temperature
Water circulation
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Experimental Conditions
Air atmosphere (20% O2, 80% N2)
Lean atmosphere (6% O2, 94% N2)
Gasification/ pyrolysis (100% N2)
Enriched atmosphere (30% O2, 70% N2)
Current conditions found in combustors
Possible enhancements for higher efficiency
Hydrogen “spiking” (3% H2, 97% N2)
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Thermal degradation for SBR in N2
Temperature, [K]
600 650 700 750 800
Wei
ght l
oss
frac
tion,
α [-
]
0.0
0.2
0.4
0.6
0.8
1.0
DTA
[1/s
ec]
0.000
0.002
0.004
0.006
0.008
0.010
0.012
β : 10K/m inβ : 20K/m inβ : 30K/m inβ : 40K/m inβ : 10K/m inβ : 20K/m inβ : 30K/m inβ : 40K/m in
( ) fraction loss Weight α=∫ dtDTA
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Combustion/Gasification Comparison
0
20
40
60
80
100
300 350 400 450 500 550 600
Temperature (oC)
Mas
s (%
)
N2 onlyair
N2
Air
10K/min
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Combustion Comparisons
Temperature (oC)
350 400 450 500 550 600
Mas
s (%
)
0
10
20
30
40
6.9% - O2Air30% - O2
30% O2
6.9% O2
Air
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Chemical Structure of SBR;25% Styrene, 75% Butadiene Cross linked Co-Polymer
1.5011.096
1.0891.342
1.547
1.087
1.396
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Gas Analysis from TGA;N2 Atmosphere, 20K/min
Temperature [oC]
200 300 400 500 600
Mas
s [%
]
0
20
40
60
80
100
Con
cent
ratio
n [P
PM]
0
100
200
300
400
500
Temperature [oC]
200 300 400 500 600
Mas
s [%
]0
20
40
60
80
100
Con
cent
ratio
n [P
PM]
0
5
10
15
20
25
n-Butane
Hydrogen
Ethylene
n-Hexane
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Hydrogen Spiking
0
20
40
60
80
100
300 350 400 450 500Temperature (oC)
% M
ass
N2 only3%_H2-N2
0
20
40
60
80
100
300 350 400 450 500Temperature (oC)
% M
ass
N2 only3%_H2-N2
10 K/minLittle enhancement
40 K/minIncreased enhancement
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Kinetic Expression Development
nkdtd )1( αα
−=( )
fi
i
WWWtW
−−
=α
−=
RTEATk n exp
( )
−−=
RTET
AdTd n exp12
10 αβ
α ( )
++
−−
= −− 1
21
2
2
2111 T
RTE
dTdn
dtd
dTd ααα
βα
( ) ( )[ ]( )( )dT
d
TRTE
dtd
dTd
nα
αααβ
−
−−−=
− 121/ 1
222
( )
−
= nTAdtd
RTEα
α
1ln
2/10
Activation Energy Calc.Reaction Order Calc.
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Kinetic Expression Development
1/Tmax [1/K]
0.00115 0.00120 0.00125 0.00130 0.00135 0.00140 0.00145 0.00150 0.00155
ln β
-2.0
-1.8
-1.6
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
Primary 100% N2
Primary 97% N2/ 3% H2
Primary airSecondary airPrimary 70%N2/ 30% O2
Secondary 70% N2/ 30%O2
2.59E+114.13E+092.30E+113.67E+12402.66E+114.24E+092.36E+113.71E+12302.72E+114.39E+092.42E+113.84E+12202.87E+114.64E+092.55E+114.02E+1210
O2 enhancedAir97% N2 + 3% H2100% N2
Factors, Ao [s-1 k-1/2]Heating rate, β [K/min]
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Summary of Kinetic Parameters
0.27 1.36 0.24 1.19 1.28AVG
0.191.160.191.061.2240
0.21.320.411.131.2630
0.241.350.351.21.320
0.431.60.011.351.3310
O2 enhancedAir97% N2 + 3% H2
Overall reaction order, n [-]Heating rate, β [K/min]
1.75E+051.84E+051.82E+051.63E+051.87E+05AVG
1.79E+051.87E+051.89E+051.65E+051.89E+0540
1.77E+051.85E+051.82E+051.64E+051.89E+0530
1.75E+051.84E+051.82E+051.62E+051.87E+0520
1.68E+051.80E+051.75E+051.60E+051.84E+0510
O2 enhancedAir97% N2 + 3% H2
Activation energy [J/mol]Heating rate, β [K/min]
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Polycyclic Aromatic Hydrocarbon (PAH)
(detected to date)
Styrene Naphthalene
Phenanthrene
Pyrene
Anthracene
Styrene
NAWTEC Conference – May 24-26, 2005, Orlando, FL
FLOWGASCHARGTIRE
OUTGAS
OUTTIRE
CHARGGAS
Aspen™ Kinetic Simulation
Combustion2
Tire + O2 CO2 + H2O ∆Hr = -35 MJ/kgBoudouard3
C(s) + CO2 2 CO ∆Hr = 11 MJ/kg
Steam reforming3
C(s) + H2O CO + H2 ∆Hr = 14 MJ/kg
Water-gas shift3
CO + H2O CO2 + H2O ∆Hr = -1.5 MJ/kg
NAWTEC Conference – May 24-26, 2005, Orlando, FL1 Reisman JI, Lemieux PM. “Air emissions from scrap tire combustion”. Clean Air Technology Center EPA, 1997.
COMBTIRE
AIR
GASTIRE
O2
FINPROD
HVQ
WATER
TOTASH
CombustorCombustor
GasifierGasifier
CalorimeterCalorimeterTire Composition1
C5H8 68% MassC 12Fe 15S 2Zn 2Ca 2
Tire Composition1
C5H8 68% MassC 12Fe 15S 2Zn 2Ca 2
Aspen™ System Simulation
Ideal ReactorIdeal ReactorIdeal MixerIdeal SeparatorIdeal MixerIdeal SeparatorIdeal ReactorIdeal SeparatorIdeal Mixer (ash)
Ideal ReactorIdeal SeparatorIdeal Mixer (ash)
Ideal HeaterIdeal ReactorIdeal Heater
Ideal HeaterIdeal ReactorIdeal Heater
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Combustion Zone
(Tire + O2 CO2 + H2O + heat)
GasificationZone
(C + H2O + CO2 + heat CO + H2 )
Syngas
Ash
Tires
Combustion-Gasification System
Slude/TireMixture
1o Air
2o Air
NAWTEC Conference – May 24-26, 2005, Orlando, FL
ConclusionThe two-stage combustion of the SBR is due to the different oxidation rates of the unsaturated hydrocarbon backbone.
Hydrogen spiking shows enhancements at high heating rates (likely found in combustors)
Simulations match closely to experiments, refinements needed
Potential for PAH formation during combustion
NAWTEC Conference – May 24-26, 2005, Orlando, FL
Future Work
Investigation will consist of GC/MS analysis of
different atmospheres.
The study of formation of Polycyclic Aromatic
Hydrocarbon (PAH) will be carried out
Further development of mechanistic understanding