Conceptual Design of Continuous Processes for

Carbon NanotubesAdedeji E. Agboola and Ralph W. Pike

Louisiana State University

Helen H. Lou, Jack R. Hopper and Carl L. YawsLamar University

Thomas A. HertwigMosaic Corporation

Paper No. 289n, American Institute of Chemical Engineers Annual Meeting, Cincinnati, Ohio Oct. 30- Nov. 4, 2005

Brief History of Carbon Nanotubes

- Discovered by Iijima and co-workers in 1991

- CNT structures consist of carbon filaments with a small diameter (nm) and a large length (µm)

- A molecular model of a single wall carbon nanotube

Properties

- High Aspect Ratio Structures - High Mechanical Strength: Tensile Strength (60 GPa) and Young Modulus (1 – 5 TPa) - High Electrical Conductivity (typically 10-6 ohm m) - High Thermal Conductivity (1750 – 5800 W/mK) - High Current Density (107 – 109 A/cm2) - Chemical Stability: (not attacked by strong acids/alkali)

Nanotube Composites

- Ideal substitutes to carbon fibers as reinforcements in high

strength, low weight and high performance composites

- Application in aerospace construction

Characteristics Carbon Fibers Carbon Nanotubes

Diameter µm nm

Strength Low High

Stiffness Low High

Density High Low

Conductivity Low High

Carbon Nanotube Laboratory Synthesis Techniques

Arc Discharge Laser Ablation CVD

Carbon Source Graphite Graphite Hydrocarbon, CO

Energy Source Electricity Laser Plasma, Furnace

Growth Temp 2500 – 3000 o C 1,200 o C 750 – 1100 o C

Yield 30 % by weight Up to 70 % 20 % - 100 %

Scalability Non – scalable Non – scalable Scalable

Advantages - Few or no

structural defects

- Diameter control

- Few Defects

- Low Temp

- Long Length

- Diameter Control

Limitations - High Temp

- Short Tubes

- Costly

- High power

- Expensive laser

- High Defects

- Low Crystallinity

Summary of Conceptual Designs of CNT Processes

CNT PFR Process CNT-FBR Process

Catalyst Fe Co – Mo

Fe(CO)5 → Fe + 5CO

Silica

Reactants CO and Fe(CO)5 CO

Reactor Type Plug Flow Reactor Fluidized Bed

Reactor Conditions 1050 oC @ 450 psi 950 oC @ 150 psi

Selectivity to CNT 90% 80%

Purification - Oxidation

- Acid Treatment

- Filtration

- Leaching

- Froth Flotation

- Acid Treatment

Production rate (kg/hr)

595 595

Process Units

Section CNT-PFR Process CNT-FBR Process

Feed

Preparation

- Mixer, Heater

- Gas Compressor

- Mixer/Heater

- Gas Compressor

Reaction - Flow Reactor

- Heat Exchangers

- Fluidized Bed

- Heat Exchangers

Purification - Filters

- Oxidizer

- Drier/Annealer

- Centrifuge

- Filters

- Flotation Column

- Drier/Annealer

- Cyclone Separator

CO Recycle - Gas Absorber

- Gas Stripper

- Gas Absorber

- Gas Stripper

CNT-PFR Process

Reactants, Product and Emissions Feed kg/hr Other kg/hr Product kg/hr Emissions kg/hr

CO 2,637 O2 253 CNT 595 FeCl2 0.07

Fe(CO5) 627 H2O 255 CO2 2,666

Fe2O3 256

H2O 255

Total Mass Flow 3,772 kg/hr Total Mass Flow 3,772 kg/hr

Energy Requirements

Steam

12,000 kg/hr

Natural Gas

486 kg/hr

Electricity

1,056 kW

CNT-FBR Process

Reactants, Product and Emission Feed kg/hr Others kg/hr Product kg/hr Emissions kg/hr

CO 3,471 O2 9 CNT 595 CO2 2,727

Mo 19 H2O 488 CoCl2 0.05 Co2O3 26

Co 19 NaOH 228 MoCl2 0.04 MoO3 28

H2O 255 NaOH 228

H2 25 CO 349

Total Mass Flow 4,234 kg/hr Total Mass Flow 4,324 kg/hr

Energy Requirements Steam

14,000 kg/hr

Natural Gas

486 kg/hr

Electricity

387 kW

CNT-PFR Process CNT-FBR Process

Production Rate 5,000,000 kg/yr 5,000,000 kg/yr

Total Plant Cost $4.6 million $4.4 million

Total Product Cost $186 million $124 million

Market Price of Carbon Fiber

$90 per kg $90 per kg

Annual Revenue $450 million $450 million

Economic Price $38 per kg $25 per kg

Net Present Value $609 million $753 million

Rate of Return 37.4% 48.2%

CNT Process using Fluidized Bed Reactor

RG2256kg/hr

SR31255kg/hr

SR322,223kg/hr

SR012,637kg/hr

SR02627kg/hr

SR0412,340kg/hr

SR1812,340kg/hr

ARout242kg/hr

SR0814,764kg/hr

SR0714,764kg/hr

SR13850kg/hr

RG1281kg/hr

SR30595kg/hr

CW252,522kg/hr

CW152,522kg/hr

SSS6,517kg/hr

BFW6,517kg/hr

ARin227kg/hr

SR272,424kg/hr

SR262,424kg/hr

SR251,763kg/hr

SR244,187kg/hr

SR292,204kg/hr

SR282,204kg/hr

SR2361,608kg/hr

SR2161,608kg/hr

SR2064,032kg/hr

SR1964,032kg/hr

SR1712,340kg/hr

SR1612,340kg/hr

SR151,967kg/hr

SR141,943kg/hr

SR122,793kg/hr

SR11825kg/hr

SR1014,764kg/hr

SR0914,764kg/hr

SR06840kg/hr

SR0515,604kg/hr

SR033,264kg/hr

V-102REACTOR

E-101GAS-FIRED

HEATER

Z-101GAS-SOLID

FILTER

E-103WASTE HEAT

BOILER

E-104COOLER

T-101GAS ABSORPTION

COLUMN

Z-102LIQUID -SOLID

FILTER

Z-103DRIER

Z-104ACID

REGENERATOR

C-101GAS

COMPRESSOR

E-105CROSS HEATEXCHANGER

T-102STRIPPINGCOLUMN

E-106REBOILER

Z-105DISCHARGE

VALVE

V-105FLASHDRUM

E-102CROSS HEATEXCHANGER

V-101MIXER

V-103OXIDIZER

V-104ACID TREAT.

TANK

Z-106CENTRIFUGE

CNT Process using Plug Flow Reactor

RG3274kg/hr

RG454kg/hr

SR34255kg/hr

SR32325kg/hr

SR31105kg/hr

SR30850kg/hr

SR29955kg/hr

Air0.01kg/hr

WS1228kg/hr

SR1316,610kg/hr

SR09379kg/hr

SR08633kg/hr

SR013,471kg/hr

RGS2373kg/hr

RGS1261kg/hr

SR33595kg/hr

CW659,089kg/hr

CW559,089kg/hr

SST7,333kg/hr

SSW7,333kg/hr

AK1228kg/hr

SR282,727kg/hr

SR272,727kg/hr

SR261,983kg/hr

SR254,710kg/hr

SR242,479kg/hr

SR232,479kg/hr

SR2269,297kg/hr

SR2069.297kg/hr

SR1972,074kg/hr

SR1872,074kg/hr

SR1713,883kg/hr

SR1613,883kg/hr

SR112,380kg/hr

SR102,491kg/hr

SR072,719kg/hr

SR063,352kg/hr

SR1516,610kg/hr

SR1416,610kg/hr

SR052,998kg/hr

SR12126kg/hr

SR0416,736kg/hr

SR0319,734kg/hr

SR0217,354kg/hr

V-201REACTOR

E-201GAS-FIRED

HEATER

Z-202GAS-SOLID

FILTER

E-202WASTE HEAT

BOILER

E-203COOLER

T-201GAS ABSORPTION

COLUMN

Z-204LIQUID-SOLID

FILTER

Z-206DRIER

Z-207CATALYST

REPLENISHMENTBED

C-201GAS COMPRESSOR

E-204CROSS HEATEXCHANGER

T-202STRIPPINGCOLUMN

E-205REBOILER

Z-209DISCHARGE

VALVE

Z-201CYCLONE

T-203FROTH

FLOTATIONCOLUMN

Z-203CENTRIFUGE

V-204FLASHDRUM

V-202LEACHING

TANK

V-203ACID

TREATMENT TANKZ-205

LIQUID-SOLIDFILTER

Z-208ACID

REGENERATOR