Prof. Gary T. Rochelle

CPE 5.462, 2 MS, 8 PhD

Projects/funding for MS or PhDTechnology Area

CO2 Capture from Flue Gas

( to address Global Climate Change)By Aqueous Absorption/Stripping

Fundamental AreasMass Transfer with Reaction in the Boundary Layer

Applied Aqueous Solution ChemistryAqueous ThermodynamicsAqueous Reaction KineticsApplied Process Simulation

CO2 Emissions by Source (1998)

Coal Elec

Gas Elec.

Petro. E

lec.

Ind. Coal

Ind. Gas

Ind. Petro

.

Trans.

Other

MM

TC

E

0

100

200

300

400

500

System for CO2 Sequestration

Boiler ESP

Flyash

FGD

CaSO4

CaCO3

Abs/Str

DisposalWell

Power

30 psia Steam

CO2

Coal

Net Power

Absorb50°C1 atm

Steam 30 psia

CO2

Strip117°C2 atm

SO2, HCl, NO

10% CO25% O212% H2O

30% MEA

Lean RichH2O

Purge to

Reclaim

MEA Absorption/Simple Stripping

C

Practical Problems• Energy = 20-40% of power plant output

– Steam for stripping– Gas pressure drop

– CO2 Compression

• Amine degradation– 10% of cost – Environmental impact

• Capital Cost– 5 x 50 ft diameter absorbers and strippers– 50 ft packing

Approaches to Practical Problems

• Better Solvents– Faster: promote by piperazine (PZ)– Evolve: Monoethanolamine (MEA)/ PZ

– Lower H: K2CO3/PZ

– Oxygen scavengers

• Better Processes– Vacuum Stripping or Vapor recompression

– CaSO4/K2SO4 Precipitation

• Better contacting– Packing to get G/L area

Fundamental Problems• Model Thermo with high salt (K+) & amine

– Electrolyte NRTL model

– Maximize solvent and CO2 concs

• Measure Mass transfer with chemical reaction

– Find feasible solvent with faster rates

• Measure oxidative degradation/corrosion– Cu++ inhibits corrosion, catalyzes degradation

*COi,CO

CO

PZPZCOOCO

22

2

2 PPH

PZkPZCOOkDFlux

Applied Problems

• Identify Packing with max area at min cost– Characterize and model wetted area

• Innovate flowsheets to minimize Q– Simulate multistage contacting– Simulate Vacuum stripping

• Control complex chemistry to minimize Q

Laboratory Projects

• Mass Transfer with chemical rxn – K2CO3/EDA

– Wetted Wall Column– NMR

• Degradation– Oxidative of Ethylenediamine– Thermal of MEA/PZ

• Solvent Reclaiming– Evaporation of PZ/MEA

– Crystallization of CaSO4 or K2SO4

Pilot Plant Projects

• Validate Models for MEA/PZ– 16.8-inch x 20 ft Absorber/stripper

• Test and Develop Innovative Packing– 16.8-inch x 10 ft PVC Absorber– Low gas velocity

• Demonstrate Process Innovations– Vacuum Stripping– Multistage contacting

Modeling Projects

• Fundamental models for K2CO3/EDA

– Thermodynamics/VLE/Speciation– Mass transfer with Chemical Reaction

• Integrated Absorber and System Models– MEA/PZ– Vacuum Stripping– Multistage stripper

• System optimization/integration– Integrate with Power Cycle

Solvent Alternatives• Functions

– Capacity by reversible reactionThermodynamics and stoichiometry

– Fast mass transfer: kinetics at interface

• Three types of chemistry– CO3

= + CO2 +H2O <> 2 HCO3-

H=5 kcal/gmol, very slow

– R3N + CO2 + H2O <> HCO3- + R3NH+

H=14 kcal/gmol, slow

– 2R2NH + CO2 <> R2N-COO- + R2NH2+

H=22 kcal/gmol, fast

N NH H

O

O

N N

O

OH N

+N

O

OH

H

N N

O

O O

O

K+

K+

O

O OO

O

O

H

H OO

OH

K+

N N

O

OH

O

O

Reaction Chemistry…

+

+ +

…For Potassium Species

…For Piperazine Species

2

+

System Solvent — 3.6 m K2CO3/0.6 m PZ

Mass Transfer

• Report as normalized flux—kg´

• Extract rate constants– Use in conjunction with NMR data– Limited by knowledge of the interface

*, 22

2

2

COiCOCO

PZPZCOOCOPP

H

PZkPZCOOkDFlux

*,

'

22 COiCOG PPkFlux gGG kKk

11

'

1

Wetted Wall Column

Gas inLiquid in

Gas out

Liquid out

ParaffinOil

PCO2

* (Pa)100 1000 10000

No

rmal

ized

Flu

x (m

ol/

Pa-

cm2 -s

)

1e-11

1e-10

5.0 M MEA

3.6 m K+/0.6 m PZ

6.2 m K+/1.2 m PZ

3.6 m K+/0.0 m PZ

Conc. K+/PZ

CO2 Absorption at 60oC

NMR Speciation Analysis

PZ(COO-)2

PZ/H+

PZCOO-/H+

3.6 m K2CO3/0.6 m PZ, T = 333K

Degradation Experiment

Oxidative Degradation

• By Oxygen in flue gas– Monethanolamine make ammonia– Piperazine makes ethylenediamine

• Dissolved metal catalyze– Fe++ – Corrosion inhibitors: Cu++, V+5

• Strip O2, add chelating agents, add oxygen scavengers

LeanSolvent

BlowerTI

TI

TI

TI

Distributor

Recycle CO2

MakeupCO2

Air Vent/makeup

C.W.15oC

CO2

Analyzer

RichSolvent

Pilot Absorber 16.8-inch ID, 20 ft of packing, SS

40 – 60oC

1 atm

Storage

Pilot Stripper16.8-inch ID, 20 ft packing, CS

Lean Solvent

Steam

Distributor

Steam

RichSolvent

CO2

Recycle

Reflux

CW

C.W.15oC

Storage

System Modeling in AspenPlus

Rate-Based contacting: RATEFRAC

Electrolyte Thermodynamics

Mass Transfer with Chemical Rxn

Simultaneous Heat Transfer

Flexible configuration and conditions

MultistageCompressor

W=7.4 kc/mol CO2

CO2130 atm

Q=20 kc/mol CO2

118 C

113 C

Multipressure Stripper

Leanldg=0.34

Richldg=0.46 115 C

4 atm

2.8 atm

2 atm