Aluminum Production and CO2 Emissions: CO2 Capture Methods and Energy Usage, Study notes of Chemistry

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Carbon Dioxide: Generation and Capture^ Jennifer L. Anthony Department of Chemical EngineeringKansas State University

Carbon Dioxide Emissions 2001^ USA24% Rest76%

Transport32%^ CommercialInd - ElecIndustrial11%19%

4% Residential6%^

Resid - Elec14% Comm - Elec14%

World – 6582 MMT

USA– 1579 MMT

In Million Metric Tons of Carbon EquivalentIndustrial – Non-Electricity / Non-Steam Cement Production^

Ammonia Synthesis

Lime Production & Use

CO2 from natural Gas

Hydrogen Production

Aluminum Production

Soda Ash Production & Use

Ethylene Oxide^

Other Chemical Processes

TOTAL^

~38 MMT^

from S. Barnicki (Eastman)

Representative CO

Emission Sources 2

Source^ % USType^ Emissions

Mole %^ TypicalCO^ inPressure^2 (psig)^ Source

Typical Capture^ Methods

Auto/Diesel^

Diffuse^ 33%

~ 13%^

0

NONE

Pulverized CoalPower

Point^ 32%

~15%^

0 NONE, Chem Abs

Nat’l Gas Power

Point^

5%^ ~ 8%

0

NONE

Integ. GasCombined Cycle(IGCC)

Point^ Small

15-65%^

800-1000^ Phys Abs; Chem Abs

Cement Manufacture

Point^

0.7%^ 9-15%

0

NONE

Ammonia Synthesis

Point^

0.7%^ 17-20%

400-550^ Phys Abs; Chem Abs

Nat’l GasSweetening

Point^ 0.3%

0.5%-10%

300-1200^ Phys Abs; Chem Abs;Membrane, < 5 MSFD

H^ Synthesis^2

Point^ 0.2%

17-20%^

400-550^ Phys Abs; Chem Abs

P-Swing Ads

Ethylene Oxide

Point^

0.015%^ 10-15%

200-^

Chem Abs from S. Barnicki (Eastman)

Conventional Fossil Fuel Steam

Power Cycle

-^ Rankine Cycle - 25-30% efficiency•^ Energy in very LPsteam is lost -condensed w/o energyrecovery•^ Difficult to controlpollution•^ Flue gas at lowpressure ~1 atm HP SteamHP Turbine^ Very LP Steam Combustor /Steam Drum

HP Generator LP Turbine LP Generator Fuel:Pulv. CoalNat'l GasPetroleum Inter-changer^ CondensateCondenser^ PostTreatment 10-20%ExcessAir

Flue Gas Blower

COH^2

O^ N 22

O 2

COAL^

15 %^ 5 %

76 %^

NAT’L GAS^

8 %^ 16 %

73 %^

COH^2

O^ N 22

O 2

COAL^

15 %^ 5 %

76 %^

NAT’L GAS^

8 %^ 16 %

73 %^

3 %from S. Barnicki (Eastman)

Conventional Methods for CO

Capture (^2) membrane

Diffusion throughmembrane; pressuregradient

Gas Permeation

Solid adsorbent

Difference in affinityfor solid

Adsorption

Reacting liquid

Preferential Reactivity

Chemical Absorption

Liquid

Preferential Solubility

Physical Absorption

SeparatingAgent

Principle ofSeparation

Method

from S. Barnicki (Eastman)

Condensate

Typical CO

Capture Process 2

Lean Gas

COOff Gas^2 CondenserSeparatorDrum StrippingColumn Reboiler

Absorber

TrimCoolerInterchanger Lean Solvent Rich Solution CO-Rich Feed Gas^2 •Many variations possible •Physical absorbent may not require extensive heat input for regeneration •CO^ off-gas often at low pressure^2 •May require pre-compression, depending on feed gas pressure

from S. Barnicki (Eastman)

Chemical Absorption

-^ Chemical reaction of absorbed CO

with solvent 2

-^ Typical absorbents:^ – Primary, secondary, tertiary, hindered amines^ •^ MEA, DEA, MDEA, TEA, 2-AMP^ – Alkali metal hydroxides or carbonates^ •^ NaOH, K

CO, Na^ CO 23 23

-^ 1st, 2nd amines limited ~0.5 mol CO

/mol Amine 2

-^ Tert & hindered can reach ~1.0 mol/mol •^ Regeneration by

∆T & often

∆^ P

-^ Solution concentration limited by solubility, corrosionand/or reactivity with O

, contaminants 2

from S. Barnicki (Eastman)

Chemical vs Physical Equilibrium^765432100 10

Chemical solvent •^ Good at low inlet P 70

CO^2

-^ Can reach very low outlet P

CO^2

i.e., < 10 ppm possible, • Sharp rise in outlet P

whenCO^2

loading reaches rxnstoichiometry Physical solvent • Better at high inlet P

CO^2

-^ Loading proportional to P

CO^2

-^ Cannot reach very low outletPi.e., usually 0.1-2%, butCO^2 some can reach ppm levels MeOH, 0°C^ MeOH, 0°C20wt% DEA, 50 °C20wt% DEA, 50 °C above Liquid, atm CO2 P CO, vol/vol absorbent^2

from S. Barnicki (Eastman)

Amine Processes

-^ Reacts with CO

to form carbamate complex 2

-^ Many commercially available processes •^ Choice dictated by removal requirements, stability tostream components •^ Generally can be selective between for H

S / CO 22

-^ Good for

P ~ 0.1 psi or higher CO^2

-^ Susceptible to O

degradation, other contaminants – 2 can be controlled • Good stage efficiencies

from S. Barnicki (Eastman)

Carbonate Processes

-^ Basic idea similar for many akali- & alkali earth hydroxides &carbonates •^ Choice dictated by cost & solubility in water •^ Non-selective between H

S / CO 2 2

-^ Very best for

P^ above ~ 10 psi, but can work at lower P CO^2

CO^2

-^ Vacuum stripping for CO

removal to less than ~ 1000 ppm 2

-^ Poor stage efficiencies – tall absorption towers •^ Improved with amine as catalyst

from S. Barnicki (Eastman)

Heat of Reaction: Representative

Absorbents

15.6^ 11.^

10.4^ 6.^

6.4^0

20.2^ 18.3 0

100 80 60 40 20 Na2CO3NaOH to

2-AMP(hindered)MEA (Prim)

(tert)MDEADEA (sec) TEA (tert)2NaHCO3Na2CO3 to

MeOH2KCO3K2CO3 to(Physical)

15.6^ 11.^

10.4^ 6.^

6.4^0

20.2^ 18.3 0

100 80 60 40 20 Na2CO3NaOH to

2-AMP(hindered)MEA (Prim)

(tert)MDEADEA (sec) TEA (tert)2NaHCO3Na2CO3 to

2KCO3MeOHK2CO3 to(Physical)

(^22) (Kcal/gmole CO(Kcal/gmole COHeat of Reaction Heat of Reaction

from S. Barnicki (Eastman)

Potential Absorbents For Flue

Gases

-^ Primary Amines

MEA (25 wt%)

-^ Secondary Amines

DEA (35 wt%), DIPA (40 wt%), DGA (40 wt%),

-^ Tertiary Amines

TEA (40 wt%), , MDEA (40 wt%),

-^ Hindered Amines

2-AMP (40 wt%), 2- iPrAMP (40 wt%),^ 30 wt% 2-BAE / 3 wt% 2-MP

-^ Mixed Amines

24 wt% MDEA / 6 wt% MEA

-^ Hot Potassium Carbonate

30 wt% Unactiv. or activ. w/ DEA, AMP

-^ Ionic Liquids

from S. Barnicki (Eastman)

Energy Usage Analysis • 15% CO^ in flue gas at ~1 atm absolute pressure^2 • 90% recovery of CO

in flue gas 2

-^ Pre-compression of flue gas to overcome pressuredrop in absorber (14.7 psia to 18 psia) •^ Post-compression of recovered CO

to 10 and 100 2

atm in two stages, w/ interstage cooling

from S. Barnicki (Eastman)

Energy Usage: CO

Capture - Compression 2^ MEA - 3.4 M BTU / Ton CO

2 Total Energy Usage for Recovery &Compression: MEA System3.4 million BTU/ton CO2 5.2%5.2%4.5%^ 85.1%

Absorption Feed Compr 1st stage - 1- 10 atm 2nd stage - 10 - 100 atm

Energy Usage for CO2 Absorption from LowPressure Flue Gas

4.7 2.5 3.2 2.8 2.3 2.

2.5^ 3.1^ 4.0^ 2.9^ 3.2^ 3. 0.0^ 1.0^ 2.0^ 3.0^ 4.

5.0^ 6.0^ 7.0^ 8. Pot Carb- AMP activPot Carb- DEA activPot Carb- no activ6% MEA/24% MDEA3% 2-MPz/30% 2-BAEMDEATEADIPA/sulfolane2-iPrAMPDGADEA2-AMPMEA^ million BTU/ton CO

P rimary A mines2nd A minesTert A minesM ixed A minesP o t Carbo nate Absorption Step

Total Energy Usage for Recovery &Compression: 2-AMP System2.8 million BTU/ton CO2 6.3%6.3%5.5%^ 81.8%

Absorption Feed Compr 1st stage - 1- 10 atm 2nd stage - 10 - 100 atm 2-AMP - 2.8 M BTU / Ton CO

2 from S. Barnicki (Eastman)