SS TSS-07 Understanding Sour System Treatment using Amines

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2 SS TSS-07 Understanding Sour System Treatment using Amines Laurie Wang, PhD, P.Eng. Invensys October 17, 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.

3 Topics Amine-based gas treating processes Amine process modeling Slide 3

4 Gas/NGL Sweetening and Treating Separation of acid gases from gas or liquid streams Sweet Gas/NGL Sour Gas/NGL Acid Gases Other impurities Acid gases: H 2 S, CO 2, SO 2 Other impurities: COS, CS 2, RSH (MeSH, EtSH), H 2 O, CO, VOCs, etc. Slide 4

5 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 Slide 5

6 Industries that need gas treating Process Natural Gas Purification Refinery Fuel Gas Treating Synthetic Gas for Chemicals Ethylene Manufacture Hydrogen Manufacture Ammonia Synthesis Common clean up targets < 4 ppm H 2 S; < 1% CO 2 < 100 ppm H 2 S < 0.01 ppm H 2 S; < 500 ppm CO 2 ~ 1 ppm H 2 S; 1 ppm CO 2 10 ppm H 2 S; < 0.1% CO 2 <16% ppm CO 2 + CO; 0.01 ppm H2S Coal Gasification 0.01 ppm H 2 S; <500 ppm CO 2 * Gas Treating with Chemical Solvents by Gianni Astarita, David Savage, and Attilio Bisio, 1983 Slide 6

7 Gas/NGL Sweetening and Treating Remove H 2 S from natural gas using amines H 2 S is Toxic and Flammable Remove COS, CS 2, Mercaptans if present Remove CO 2 if economically favorable Common operating problems: Corrosion at high temperatures / concentration Foaming Amine losses entrainment loss degradation loss solubility loss vaporization loss Slide 7

8 Gas/NGL Treating Technologies Aqueous alkanolamines (chemical solvents) Physical solvents (physical absorption) Physical-Chemical blended solvents Carbonate process Others Molecular sieves Membranes Extractive distillations Slide 8

9 Technology Based Gas Treating Facilities 80% 70% 60% 50% 40% 30% 20% 10% 0% Capacity Chem. Solvents Phy. Solvents Direct Convn Ext. Dist. Mol. Sieve Membranes Unknown Plants * Schlumberger DBR Slide 9

10 Chemical Solvents Aqueous Amines MEA Monoethanolamine DEA Diethanolamine MDEA - Methyldiethanolamine DGA Diglycolamine DIPA Diisopropanolamine TEA - Triethanolamine Slide 10

11 Trends in Gas Treating Technology using Amines DEA MEA MDEA Proprietary Solvents * Schlumberger DBR Slide 11

12 Molecular Structures of Common Amines Amines are derivatives from ammonia with one or more of its hydrogen atoms being replaced by a substituent, such as an alkyl or aryl group In Primary Amines, only one of the hydrogen atoms in the ammonia molecule is replaced In Secondary Amines, two of the hydrogen atoms in the ammonia molecule are replaced In Tertiary Amines, all three hydrogen atoms in the ammonia molecule are replaced Slide 12

13 Molecular Structures of Common Amines Primary Amines Monoethanolamine (MEA) Diglycolamine (DGA) H H NCH 2 CH 2 OH H H NC 2 H 4 OC 2 H 4 OH Slide 13

14 Molecular Structures of Common Amines Secondary Amines Diethanolamine (DEA) Diisopropanolamine (DIPA) H N CH 2 CH 2 OH CH 2 CH 2 OH H N CH 3 CH 2 CHOH CH 2 CHOH CH 3 Slide 14

15 Molecular Structures of Common Amines Tertiary Amines Methyldiethanolamine (MDEA) Triethanolamine (TEA) CH 2 CH 2 OH CH 2 CH 2 OH CH3 N HOCH 2 CH 2 N CH 2 CH 2 OH CH 2 CH 2 OH Slide 15

16 Pros and Cons of Amines 1-/2- Amine (MEA / DEA) Advantage Fast reaction Low solvent cost Thermal stable Disadvantage Lack of selectivity High energy cost Highly corrosive 3- Amine (MDEA) Selectivity Less energy cost Less corrosive High resistance to degradation Slow reactions with CO 2 High solvent cost Minimal COS/CS 2 removal Slide 16

17 Physical Solvents Water Methanol (trade name Rectisol by Linde and Lurgi) DEPG, dimethyl ethers of polyethylene glycol, (Selexol by Union Carbide, 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 Solvent TM ) Slide 17

18 Pros and Cons of Physical Solvents Advantage Little heat needed for solvent recovery Low operating costs Treatment of high acid gas contents Possible for simultaneous gas dehydration Disadvantage High capital cost High solvent cost Slide 18

19 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) Slide 19

20 Acid Gases with Amine Solutions H 2 S: Bronsted acid (gives proton) 2 RNH 2 + H 2 S = (RNH 2 ) 2 H 2 S A very fast kinetics CO 2 : Lewis acids (accepts electron) R 1 R 2 NH + CO 2 = R 1 R 2 NCOO - + H + CO 2 + H 2 O = H + + HCO - 3 Chemical reaction equilibrium involved Slide 20

21 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 H 2 S but not CO 2 Mixtures of different amines Slide 21

22 Typical Amine Treating Process Lean amine removes H 2 S and CO 2 from natural gas in the contactor at low T H 2 S and CO 2 are removed from rich amine in regenerator at high temperature Slide 22

23 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 Slide 23

24 Amine Treating Process Modeling Using PRO/II AMINE package Support single amine system, such as MEA, DEA, DGA, DIPA, and MDEA Dimensionless residence time corrections to amine K-value calculation may be specified by user for systems involving MDEA or DGA. Slide 24

25 Amine Treating Process Modeling Using PRO/II OLI Electrolyte package For single amine systems Use ELDIST or RATERFAC algorithms Slide 25

26 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 Slide 26

27 Thermodynamic Framework in AMSIM Phase Equilibrium (VLE & LLE) Chemical Reaction Equilibrium Mass Balance Electroneutrality Slide 27

28 Thermodynamic Methods in AMSIM Kent-Eisenberg Model, 1976 (Empirical) Ideal Solution: = 1 Equilibrium constants tuned against experimental data Li-Mather Model (Electrolyte Model), 1994 K ( i x i Azk I ln k b I k ) i i j kj m j Slide 28

29 Using AMSIM in PRO/II AMSIM is a unit operation in PRO/II Slide 29

30 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 the flowsheet Slide 30

31 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 Slide 31

32 Working With AMSIM Project Setup is where you define base configuration Slide 32

33 Working With AMSIM Component Selection Slide 33

34 Working with AMSIM (cont.) Select a red box to add/remove optional equipment Slide 34

35 Working With AMSIM (cont.) Click on Enter Data button and click on items to enter data Slide 35

36 Using AMSIM in PRO/II (cont.) Click on Run button or Run from PRO/II Run menu Slide 36

37 Warning on Thermodynamics AMSIM thermodynamics are NOT identical to PRO/II ensure outlet conditions are set properly in AMSIM unit operation Slide 37

38 Gas Treating with MEA Absorber High Pres Low Temp Sweet Gas Almost no H 2 S Sour Gas 1 5 Cooler Lean Amine < 15 wt% MEA Rich Amine 0.5 mole acid gas/mole MEA MEA and Water loss Makeup Anti-Corrosion measures Acid Gas Regenerator High Temp Low Pres 10 Slide 38

39 Gas Treating Demo 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) = 0.5 MW of MEA =61 ; 15% by weight MEA 3. Simulate the absorber using AMSIM 4. Add controller to impose the acid gas pickup specification 5. Add hydrocarbon purge valve and Feed-Btms exchanger 6. Add the regenerator using AMSIM 7. Setup Makeup Stream Calculator 8. Close the recycle loop Slide 39

40 Details 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 Slide 40

41 Known Information 75 F 7.5 psig 22.2 psia 120 F 7 psig 21.7 psia 230 psig 244.7psia 100 F 230 psig 15wt% MEA 8 psig 22.7 psia Molar reflux ratio=4 Sour gas feed psig psia 0.5 mole acid gas/mole MEA 10 psig 24.7 psia ΔP=2psi 180 F 9.5 psig 24.2 psia psia Slide 41

42 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 Slide 42

43 Recommended Procedure (cont.) Click on Enter Data button Enter stream and column information Save and exit (automatically creates PRO/II components and streams) 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 existing streams Slide 43

44 Thank You for Attending This Session For Technical Support SIMSCI-1 ( ) Slide 44

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