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SS TSS-07 Understanding Sour SystemTreatment using Amines

Laurie Wang, PhD, P.Eng.InvensysOctober 17, 2013

© 2013 Invensys. All Rights Reserved. The names, logos, and taglines identifying the products and services of Invensys are proprietary marks of Invensys or its subsidiaries.All third party trademarks and service marks are the proprietary marks of their respective owners.

Laurie Wang, PhD, P.Eng.InvensysOctober 17, 2013

Topics

• Amine-based gas treating processes

• Amine process modeling

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Gas/NGL Sweetening and Treating

• Separation of acid gases from gas or liquid streams

Acid gases: H2S, CO2, SO2

Other impurities: COS, CS2, RSH (MeSH, EtSH), H2O, CO, VOCs, etc.

Sour Gas/NGL Acid Gases

Sweet Gas/NGL

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• Separation of acid gases from gas or liquid streams

Acid gases: H2S, CO2, SO2

Other impurities: COS, CS2, RSH (MeSH, EtSH), H2O, CO, VOCs, etc.

Other impurities

Gas/NGL Sweetening and Treating

• Importance of acid gas removal

• Maintain safe environment from poisonous materials

• Prevent equipment and pipeline corrosion

• Prevent catalyst poisoning

• Maintain heating value

• Further chemical process

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• Importance of acid gas removal

• Maintain safe environment from poisonous materials

• Prevent equipment and pipeline corrosion

• Prevent catalyst poisoning

• Maintain heating value

• Further chemical process

Industries that need gas treatingProcess Common clean up targets

Natural GasPurification

< 4 ppm H2S; < 1% CO2

Refinery Fuel GasTreating

< 100 ppm H2S

Synthetic Gas forChemicals

< 0.01 ppm H2S; < 500 ppm CO2

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Synthetic Gas forChemicalsEthyleneManufacture

~ 1 ppm H2S; 1 ppm CO2

HydrogenManufacture

10 ppm H2S; < 0.1% CO2

Ammonia Synthesis <16% ppm CO2 + CO; 0.01 ppmH2S

Coal Gasification 0.01 ppm H2S; <500 ppm CO2

* Gas Treating with Chemical Solvents by Gianni Astarita, David Savage, and Attilio Bisio, 1983

Gas/NGL Sweetening and Treating

• Remove H2S from natural gas using amines• H2S is Toxic and Flammable

• Remove COS, CS2, Mercaptans if present

• Remove CO2 if economically favorable

• Common operating problems:

• Corrosion at high temperatures / concentration

• Foaming

• Amine losses• entrainment loss

• degradation loss

• solubility loss

• vaporization loss

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• Remove H2S from natural gas using amines• H2S is Toxic and Flammable

• Remove COS, CS2, Mercaptans if present

• Remove CO2 if economically favorable

• Common operating problems:

• Corrosion at high temperatures / concentration

• Foaming

• Amine losses• entrainment loss

• degradation loss

• solubility loss

• vaporization loss

Gas/NGL Treating Technologies

• Aqueous alkanolamines (chemical solvents)

• Physical solvents (physical absorption)

• Physical-Chemical blended solvents

• Carbonate process

• Others• Molecular sieves

• Membranes

• Extractive distillations

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• Aqueous alkanolamines (chemical solvents)

• Physical solvents (physical absorption)

• Physical-Chemical blended solvents

• Carbonate process

• Others• Molecular sieves

• Membranes

• Extractive distillations

Technology Based Gas Treating Facilities

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Chem

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* Schlumberger DBR

Chemical Solvents – Aqueous Amines• MEA – Monoethanolamine

• DEA – Diethanolamine

• MDEA - Methyldiethanolamine

• DGA – Diglycolamine

• DIPA – Diisopropanolamine

• TEA - Triethanolamine

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• MEA – Monoethanolamine

• DEA – Diethanolamine

• MDEA - Methyldiethanolamine

• DGA – Diglycolamine

• DIPA – Diisopropanolamine

• TEA - Triethanolamine

Trends in Gas Treating Technologyusing Amines

MDEAMDEA

ProprietaryProprietarySolventsSolvents

19401940 19501950 19601960 19701970 19801980 19901990 20002000

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MEAMEADEADEA

MDEAMDEA

ProprietaryProprietarySolventsSolvents

* Schlumberger DBR

Molecular Structures of Common Amines

• Amines are derivatives from ammonia with one or more of itshydrogen atoms being replaced by a substituent, such as an alkyl oraryl group

• In Primary Amines, only one of the hydrogen atoms in the ammoniamolecule is replaced

• In Secondary Amines, two of the hydrogen atoms in the ammoniamolecule are replaced

• In Tertiary Amines, all three hydrogen atoms in the ammoniamolecule are replaced

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• Amines are derivatives from ammonia with one or more of itshydrogen atoms being replaced by a substituent, such as an alkyl oraryl group

• In Primary Amines, only one of the hydrogen atoms in the ammoniamolecule is replaced

• In Secondary Amines, two of the hydrogen atoms in the ammoniamolecule are replaced

• In Tertiary Amines, all three hydrogen atoms in the ammoniamolecule are replaced

Molecular Structures of Common Amines

H

Primary Amines

Monoethanolamine (MEA)

H

Diglycolamine (DGA)

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H

HNCH2CH2OH

H

HNC2H4OC2H4OH

Molecular Structures of Common Amines

Secondary Amines

Diethanolamine (DEA)

CH2CH2OH

Diisopropanolamine (DIPA)

CH2CHOHCH3

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NCH2CH2OH

CH2CH2OHH N

CH2CHOH

CH2CHOHH

CH3

Methyldiethanolamine (MDEA)

Molecular Structures of Common Amines

Tertiary Amines

CH2CH2OH

Triethanolamine (TEA)

CH2CH2OH

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CH3 N

CH2CH2OH

CH2CH2OH

NCH2CH2OH

CH2CH2OHHOCH2CH2

Pros and Cons of Amines

Advantage Disadvantage1-/2- Amine(MEA / DEA)

• Fast reaction• Low solvent cost• Thermal stable

• Lack of selectivity• High energy cost• Highly corrosive

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• Fast reaction• Low solvent cost• Thermal stable

• Lack of selectivity• High energy cost• Highly corrosive

3- Amine(MDEA)

• Selectivity• Less energy cost• Less corrosive• High resistance to degradation

• Slow reactions with CO2• High solvent cost• Minimal COS/CS2 removal

Physical Solvents

• Water

• Methanol (trade name Rectisol by Linde and Lurgi)

• DEPG, dimethyl ethers of polyethylene glycol, (Selexol by UnionCarbide, DOW, UOP, and Coastal by AGR)

• Tetramethylene sulfone (Sulfolane by Shell)

• Glycols (EG, DEG, and TEG)

• NMP, n-methyl pyrrolidone (Purisol by Lurgi)

• Propylene Carbonate (Flour SolventTM)

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• Water

• Methanol (trade name Rectisol by Linde and Lurgi)

• DEPG, dimethyl ethers of polyethylene glycol, (Selexol by UnionCarbide, DOW, UOP, and Coastal by AGR)

• Tetramethylene sulfone (Sulfolane by Shell)

• Glycols (EG, DEG, and TEG)

• NMP, n-methyl pyrrolidone (Purisol by Lurgi)

• Propylene Carbonate (Flour SolventTM)

Pros and Cons of Physical Solvents

Advantage Disadvantage

• Little heat needed for solvent recovery• Low operating costs• Treatment of high acid gas contents• Possible for simultaneous gas dehydration

• High capital cost• High solvent cost

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• Little heat needed for solvent recovery• Low operating costs• Treatment of high acid gas contents• Possible for simultaneous gas dehydration

Proprietary Solvents

• Sulfinol-D, Sulfinol-M, Sulfinol-X (Shell)

• Selexol (Union Carbide)

• Flexsorb (Exxon)

• TEX-TREATS (Huntsman)

• UCARSOLS (Union Carbide)

• GAS/SPEC (DOW)

• MDEA (BASF)

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• Sulfinol-D, Sulfinol-M, Sulfinol-X (Shell)

• Selexol (Union Carbide)

• Flexsorb (Exxon)

• TEX-TREATS (Huntsman)

• UCARSOLS (Union Carbide)

• GAS/SPEC (DOW)

• MDEA (BASF)

Acid Gases with Amine Solutions

H2S: Bronsted acid (gives proton)2 RNH2 + H2S = (RNH2)2 H2SA very fast kinetics

CO2: Lewis acids (accepts electron)R1R2NH + CO2 = R1R2NCOO- + H+

CO2 + H2O = H++ HCO3-

Chemical reaction equilibrium involved

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H2S: Bronsted acid (gives proton)2 RNH2 + H2S = (RNH2)2 H2SA very fast kinetics

CO2: Lewis acids (accepts electron)R1R2NH + CO2 = R1R2NCOO- + H+

CO2 + H2O = H++ HCO3-

Chemical reaction equilibrium involved

Acid Gases with Amine Solutions

• At low temperatures, amines absorb acid gas

• High temperatures favor desorption

• Mono- and di-ethanol-amine commonly used

• MDEA removes H2S but not CO2

• Mixtures of different amines

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Typical Amine Treating Process

Lean amine removesH2S and CO2 fromnatural gas in thecontactor at low T

H2S and CO2 areremoved from richamine in regeneratorat high temperature

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Lean amine removesH2S and CO2 fromnatural gas in thecontactor at low T

H2S and CO2 areremoved from richamine in regeneratorat high temperature

Benefits of Amine Treating Process Modeling

• Increase design certainty

• Evaluate various process configurations/different types of solvents

• Assess energy costs

• Predict the purity of products

• Determine the size of equipment

• Troubleshoot and pinpoint problems

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• Increase design certainty

• Evaluate various process configurations/different types of solvents

• Assess energy costs

• Predict the purity of products

• Determine the size of equipment

• Troubleshoot and pinpoint problems

Amine Treating Process Modeling

• Using PRO/II AMINE package

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– Support single amine system, such as MEA, DEA, DGA, DIPA, and MDEA

– Dimensionless residence time corrections to amine K-value calculationmay be specified by user for systems involving MDEA or DGA.

Amine Treating Process Modeling

• Using PRO/II OLI Electrolyte package

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– For single amine systems

– Use ELDIST or RATERFAC algorithms

Acid Amine Process Modeling

• Using AMSIM technology from Schlumberger DBR via PRO/II

– Developed by D. B. Robinson and Associates in the 1980’s

– Stand-alone simulator

– Available as a module embedded within PRO/II

– Single or any combination of two blended amines

– Physical Solvent Model (DEPG)

– Non-equilibrium stage model with different column configurations

– Simulation of gas or LPG treating processes

– Mercaptans and COS removal based on in-house measured data

– VLLE (3-Phase) flash calculation

– Aromatics components (BTEX) supported

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• Using AMSIM technology from Schlumberger DBR via PRO/II

– Developed by D. B. Robinson and Associates in the 1980’s

– Stand-alone simulator

– Available as a module embedded within PRO/II

– Single or any combination of two blended amines

– Physical Solvent Model (DEPG)

– Non-equilibrium stage model with different column configurations

– Simulation of gas or LPG treating processes

– Mercaptans and COS removal based on in-house measured data

– VLLE (3-Phase) flash calculation

– Aromatics components (BTEX) supported

http://www.slb.com/services/characterization/core_pvt_lab/fluid_lab_services/fluid_lab_software.aspx

• Phase Equilibrium (VLE & LLE)

• Chemical Reaction Equilibrium

• Mass Balance

• Electroneutrality

Thermodynamic Framework in AMSIM

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• Kent-Eisenberg Model, 1976 (Empirical)

• Ideal Solution: = 1

• Equilibrium constants tuned against experimental data

• Li-Mather Model (Electrolyte Model), 1994

Thermodynamic Methods in AMSIM

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Using AMSIM in PRO/II• AMSIM is a unit operation in PRO/II

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Simulation Options• Simulate the entire unit in AMSIM and pass only net feeds and

products to PRO/II

• Simulate individual columns in AMSIM and let PRO/II solve theflowsheet

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Working with AMSIM• Each AMSIM unit has its own file (.apj) which is used to store

configuration information

• This file is zipped along with *.prz file

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Working With AMSIM• Project Setup is where you define base configuration

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• Component Selection

Working With AMSIM

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Working with AMSIM (cont.)

• Select a red box to add/remove optional equipment

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Working With AMSIM (cont.)

• Click on Enter Data button and click on items to enter data

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Using AMSIM in PRO/II (cont.)

• Click on Run button or Run from PRO/II Run menu

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Warning on Thermodynamics• AMSIM thermodynamics are NOT identical to PRO/II – ensure

outlet conditions are set properly in AMSIM unit operation

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Gas Treating with MEA

2

1

1

AbsorberHigh PresLow Temp

RegeneratorHigh TempLow Pres

Lean Amine< 15 wt% MEA

Sweet GasAlmost no H2S

Acid GasMakeupCooler

MEA andWater loss

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95

AbsorberHigh PresLow Temp

RegeneratorHigh TempLow Pres

Lean Amine< 15 wt% MEA

Sour Gas10

Rich Amine0.5 mole acid gas/mole MEA Anti-Corrosion

measures

Gas Treating DemoSteps:1. Add component data and thermo data (use Amine)2. Estimate the Lean Amine Recycle Rate (using Excel)

(moles acid gas/moles of MEA) = 0.5MW of MEA =61 ; 15% by weight MEA

3. Simulate the absorber using AMSIM4. Add controller to impose the acid gas pickup specification5. Add hydrocarbon purge valve and Feed-Btms exchanger6. Add the regenerator using AMSIM7. Setup Makeup Stream Calculator8. Close the recycle loop

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Steps:1. Add component data and thermo data (use Amine)2. Estimate the Lean Amine Recycle Rate (using Excel)

(moles acid gas/moles of MEA) = 0.5MW of MEA =61 ; 15% by weight MEA

3. Simulate the absorber using AMSIM4. Add controller to impose the acid gas pickup specification5. Add hydrocarbon purge valve and Feed-Btms exchanger6. Add the regenerator using AMSIM7. Setup Makeup Stream Calculator8. Close the recycle loop

Step 2: Lean Amine recycle rate estimate?

• You know its Temperature and Pressure

• Composition is approximately 15 wt % MEA, 85% water

• Determine rate from acid gas pickup spec

• Acid gas in feed / MEA in rich amine = 0.3 mole ratio

Step 4: How to impose the acid gas pickup specification?

• Use a controller to impose acid gas pickup specification

• Vary the lean amine flow rate

Details

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Step 2: Lean Amine recycle rate estimate?

• You know its Temperature and Pressure

• Composition is approximately 15 wt % MEA, 85% water

• Determine rate from acid gas pickup spec

• Acid gas in feed / MEA in rich amine = 0.3 mole ratio

Step 4: How to impose the acid gas pickup specification?

• Use a controller to impose acid gas pickup specification

• Vary the lean amine flow rate

Known Information

230 psig244.7psia 100°F

230 psig15wt% MEA

75°F7.5 psig22.2 psia

8 psig22.7 psia

Molarrefluxratio=4

120°F7 psig21.7 psia

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Sour gas feed

249.7 psia

231.5 psig246.2 psia

0.5 mole acid gas/mole MEA10 psig24.7 psia

180°F

ΔP=2psi

9.5 psig24.2 psia

Recommended Procedure• Add AMSIM unit

• Open AMSIM unit and start AMSIM GUI

• Select Project | Setup and configure base configuration

– Model selection

– Solvent selection

– Feed selection

– Flowsheet Selection

– Component selection

• Add/remove optional equipment on the AMSIM PFD

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• Add AMSIM unit

• Open AMSIM unit and start AMSIM GUI

• Select Project | Setup and configure base configuration

– Model selection

– Solvent selection

– Feed selection

– Flowsheet Selection

– Component selection

• Add/remove optional equipment on the AMSIM PFD

Recommended Procedure (cont.)

• Click on Enter Data button

– Enter stream and column information

• Save and exit (automatically creates PRO/II components andstreams)

• Run

• After successful solution one can connect to existing PRO/II streams

– Do not remove feed/product streams from AMSIM unit

– Use a dummy unit-op (valve with zero DP) if necessary to join to existingstreams

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• Click on Enter Data button

– Enter stream and column information

• Save and exit (automatically creates PRO/II components andstreams)

• Run

• After successful solution one can connect to existing PRO/II streams

– Do not remove feed/product streams from AMSIM unit

– Use a dummy unit-op (valve with zero DP) if necessary to join to existingstreams

Thank You for Attending This Session

For Technical Support

1-800-SIMSCI-1 (1-800-746-7241)

Email: support.simsci@invensys.com

laurie.wang@invensys.com

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For Technical Support

1-800-SIMSCI-1 (1-800-746-7241)

Email: support.simsci@invensys.com

laurie.wang@invensys.com

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