Investigation of Thermo-Gravimetric Analysis (TGA) on Waste Tires and Chemical Analysis Including Light Hydrocarbon, Substituted

Aromatics, and Polycyclic Aromatic Hydrocarbon (PAH)

Eilhann KwonDepartment of Earth and Environmental Engineering (HKSM)

Columbia University, New York, NY, 10027

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Presentation Outline

• Introduction & Background• Experimental Setup• Previous work• Results• Conclusions & Future Work

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Objectives

• Characterize the thermal degradation mechanisms of a waste tire in the combustion and pyrolysis process

• Identify by-products from the thermal degradation of a waste tire

• Investigate air pollutant generation mechanism from the combustion and pyrolysis process

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Feasibility of Waste tires as fuel

Heating Value of Fuels*

Fuel Heating Value (Btu/lb) Peat 2,500-6,500Wood 6,500Coal 8,000-14,500

Gasoline 20,400Diesel 19,300

Tire 12,000-16,000

* Source: NIST Chemistry WebBook

OilofBarrelmillionyrBTUnquadrillio

lblbBTU

12/ 09.0

1029320000,15 6

≈≈

×××≈

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Assumption• Avg. Wt. of a waste tire: 20lbs• Experimental heating value of a waste

tire: 15,000Btu/lb• Waste Tire generation a year: 293million

Introduction

Landfill/Stockpile• 75% Void Volume

– Needs high cost of tipping fees– Leads to extremely difficult conditions

for quenching tire fires– Causes the piercing the landfilling cover

• Non-biodegradability• Leachate

Waste tire generation (293 million waste tires in U.S.)1 waste tire / 1 person / 1 year

Utilization Alternatives(Combustion & Gasification/Pyrolysis)

LandfillStockpiles

LandfillStockpiles

CombustionPyrolysis

Recycle

Recycle

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Source: EPA & Rubber Manufacturer Association

Overall Experimental Setup

15th NAWTEC, MAY 21-23, 2007, Miami, FL

N2

80ml/min

20ml/min

Heated tubing (280oC)

Micro-GC & GC/MS

Mass Flow Controller

Certified gases (pure and mixtures)

Const. Temperature

Water circulation

O2 Air

Experimental ConditionsCurrent conditions found in combustors

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Air atmosphere (21% O2, 79% N2)

Lean atmosphere (7% O2, 93% N2)

Gasification/ pyrolysis (100% N2)

Enriched atmosphere (30% O2, 70% N2)

Possible enhancements for higher efficiency

Properties of a Tire

Cross section of a tire Main constituents of rubber(Approximately 60%)

C C

CH2

H3C

H2C

H

**

n

*

HC

CH

H2C

CH2

HC

CH

H2C

CH2

CHCH2

H2C

CH

HC

*

n

C C

CH2

H

H2C

H

**

n

Natural Rubber(Poly-Isoprene)

Butyl Rubber

Styrene-Butadiene Rubber (SBR)25 wt% of Styrene+75wt% of Butadiene

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Previous Work

Thermo-gram of SBR and IR in various atmospheres at 20oC/min heating rate

15th NAWTEC, MAY 21-23, 2007, Miami, FL

SBR IR

Wei

ght L

oss F

ract

ion,

α[-

]

Wei

ght L

oss F

ract

ion,

α[-

]

Location of Epoxyethane in the Region of the Decomposition Plateau

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Marco J. Castaldi and Eilhann Kwon, “Beneficial Use of Waste Tires: An Integrated Gasification and Combustion Process Design via Thermo-Gravimetric Analysis (TGA) of Styrene-Butadiene Rubber (SBR) and Poly-Isoprene (IR)”, EES , In pressing, 2007

Characterization of Thermal Degradation of Tires

Temperature, [oC]

0 200 400 600 800 1000

Wei

ght L

oss,

[%]

0

20

40

60

80

100

100% N2 Atmosphere7% O2 & 97% N2

Air Atmosphere30% O2 & 70% N2

Heating rate: 10oC/min

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Volatilization + Oxidation

SEM/EDX Analysis

1000oC in N2 500oC in lean air 700oC in lean air 1000oC in lean air

Temperature (oC) Atmosphere C Wt % S Wt%25oC air 94.14% 2.6%

1000oC N2 93.19% NA500oC 7% O2 & Bal. N2 93.48% NA700oC 7% O2 & Bal. N2 88.15% NA

1000oC 7% O2 & Bal. N2 31.42% NA

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Chromatogram from a Tire at 400oC in N2 Atmosphere

Chromatogram from SBR Chromatogram from IR

Chromatograms from the thermal degradation of a Tire

Isoprene

Toluene EthylbenzeneStyrene

Styrene

1-methyl-4-(1-methylethyl)-benzene

Limonene

Limonene

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Concentration Profiles of Styrene & Limonene

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Heating rate: 20oC/min

Proposed Limonene Formation MechanismEquilibrium geometry based on Hartree-Fock approximations using the 3-21G method

Modeling using SPARTAN, Wavefunction Inc.

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Chromatogram from IR in N2 Atmosphere

Isoprene

Limonene

Qualitative GC/MS Results from a tire in Air

Chemical Species (M.W) Chemical Species (M.W)

Methane (16) 2-methyl-1-buten-3-yne (66)

Acetylene (26) Octane (114)

Ethane (30) 4-octene (112)

Propane (44) n-dodecane (170)

n-Butane (58) Ethanol (46)

But-1-ene (56) Cyclohexanol (112)

1,3-butadiene (54) 1-pentanol (88)

Pentane (72) 1-cyclopropyl-ethanone (84)

1-pentene (70) Octanal (142)

1,4-pentadiene (68) Propanone (142)

Hexane (86) Acetone (58)

1-Hexene (84) 2-Decanol (158)

Cyclohexene (82) 1,3-Butadienal (68)

1,1-dimethyl-cyclopropane (72) 3-Butene-2-one (70)

3-methyl-2-pentene (84) Buanone (72)

2-methyl-1-pentene (84) Hexanol (102)

1-methyl-cyclopentene (82) 3-Methyl Butanol (88)

4-methyl-cyclopentene (82) Thiophene (84)

Cyclopentene (68) Benzoic Acid (122)

2-pentyne (68) Benzaldehyde (106)

Hydrocarbons

Partial OxidationAlcohol

Aldehyde

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Concentration Profiles of Phenol in Various Atmospheres

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Concentrations of Chemical Release from a TGA Unit with a Tire at heating rate 10oC/min in air

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Concentration Profiles of Phenyl-C2-3 and Phenyl-C4from a tire in 30% O2 and Bal. N2 Atmosphere

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Precursors to the formation of PAHStructure breakdownGas phase addition of reactive

intermediates

Hexylbenzene

1,2,4-triethylbenzene

1,3,5-triethylbenzene

Concentration Profiles of Phenyl-C6 from a tire in 7% O2 and Bal. N2 Atmosphere

15th NAWTEC, MAY 21-23, 2007, Miami, FL

The Origin of Benzene DerivativesMain pathway to form benzene derivatives from SBR

15th NAWTEC, MAY 21-23, 2007, Miami, FL

The Origin of Benzene Derivatives

Diels-Alder Reaction

From the thermal degradation of IR

Diels-Alder ReactionFrom SBR backbone

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Concentration Profiles of Naphthalene with a Tire in Various Atmospheres

15th NAWTEC, MAY 21-23, 2007, Miami, FL

CH3

H3C

CH3

H3C

H3C

Concentration Profiles of 2 and 3 ring at 10oC/min Heating Rate in Air Atmosphere

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Conclusions

• Volatilization and combustion was observed simultaneously when oxygen presented.

• The bond scission followed by hydrogenation was observed in monomer of main constituents of a tire

• The Hierarchical step for growing benzene derivatives by gas phase addition also observed.

• The oxidized benzene derivatives such as phenol reached up to 30PPMV in enhanced air atmosphere and the secondary oxidized chemical species derived from phenol such as benzaldehyde were observed.

• Oxidation is the feasible way to reduce the level of hazardous air pollutants including VOCs and PAHs.

• The chemical analysis from different ratio between SBR and IR in various atmospheres should be carried out.

15th NAWTEC, MAY 21-23, 2007, Miami, FL

Future Work

• Determine and develop the higher efficiency and lower emission firing technology.

15th NAWTEC, MAY 21-23, 2007, Miami, FL

AcknowledgementMarco J. Castaldi

15th NAWTEC, MAY 21-23, 2007, Miami, FL