thermo-gravimetric analysis (tga) of combustion and ... · nawtec conference – may 24-26, 2005,...

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


PresentationIntroduction

Experimental Setup

ResultsExperimental

Modeling

Conclusions

Future Work


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


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


Experimental SetupTire Composition

Natural RubberPoly-isoprenesCarbon BlackSulfurInerts and metals

Major synthetic rubbersStyrene Butadiene Rubber (SBR)Styrene rubber (SR)Butadiene Rubber (BR)


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


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)


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


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


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


Chemical Structure of SBR;25% Styrene, 75% Butadiene Cross linked Co-Polymer

1.5011.096

1.0891.342

1.547

1.087

1.396


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


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


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.


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]


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]


Polycyclic Aromatic Hydrocarbon (PAH)

(detected to date)

Styrene Naphthalene

Phenanthrene

Pyrene

Anthracene

Styrene


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


Simulation Results

Combustion Gasification


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


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


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


AcknowledgementsEilhann Kwon – PhD Student

Brian Wiess – Undergraduate EEE student

thermo-gravimetric analysis (tga) of combustion and ... · nawtec conference – may 24-26, 2005,...

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