CO 2 Capture by Amine Scrubbing

Transcription

1 CO 2 Capture by Amine Scrubbing By Gary T. Rochelle Luminant Carbon Management Program Department of Chemical Engineering The University of Texas at Austin Workshop on CO 2 Capture UNAM, Mexico City, March 28, 2012

2 Central Messages Amine Scrubbing is THE technology for CO 2 capture from Coal Power plants Energy consumption by amines is approaching 20 % of the plant output, a practical lower limit. Solvent degradation & contamination will probably limit the chemical cost to less than $5/lb.

3 40% of US CO 2 emissions are From Electricity Generation 78%

4 CO 2 Capture & Storage Disposal Well Net Power 3-6 atm stm 150 atm CO 2 Coal Turbines Boiler -NO x ESP CaCO 3 FGD Abs/Str NH 3 Flyash CaSO 4

5 Amine Scrubbing (Bottoms, 1930) 30 wt% MEA CO 2 Packed Absorber 1 bar DT=5C Stripper 2 bar Packing or Trays 12% CO 2 5% O 2 0 ppm SO 2 40 o C 115C Reboiler 45 psig stm

6 Aqueous Abs/Str: Near commercial 100 s of plants for treating H 2 & natural gas MEA and other amine solvents No oxygen 10 s of plants with combustion of natural gas Variable oxygen, little SO 2 Fluor, 30% MEA, 80 MW gas, 15% O 2 MHI, KS-1, 30 MW, <2% O 2 A few plants with coal combustion Abb-Lummus, 20% MEA, 6, 8, & 33 MW Fluor, 30% MEA, 3 small pilots, 5 MW CASTOR, 30% MEA, 1 MW pilot MHI, KS-1, <1 MW pilot, 25 MW

7 Tail End Technology Ideal for Development, Demonstration, & Deployment Low risk Independent, separable, add-on systems Allows reliable operation of the existing plant Failures impact only Capture and Sequestration Low cost & less calendar time Develop and demonstrate with add-on systems Not integrated power systems as with IGCC Reduced capital cost and time Resolve problems in small pilots with real gas Demo Full-scale absorbers with 100 MW gas Ultimately 500 MW absorbers

8 Other Solutions for Coal Oxy-Combustion O 2 plant & compression require more energy Gas recycle, boiler modification for high CO 2 Gas cleanup, compression including air leaks Coal Gasification / Combined Cycle O 2 plant, complex gasifier, cleanup, CO 2 removal Not ready for deployment Relatively more expensive on PRB or lignite New plants only Neither is Tail end: More suitable for new plants Require higher development cost, time, and risk Not suitable for on/off to address peaking

9 Practical Problem is Cost $40-70/ton CO 2 removed = $40-70/MWh Issues of absorption/stripping Energy = 20-30% of power plant output $20/ton CO 2 Theoretical Minimum is 11% Capital Cost $ /kw Absorber for 500 MW:20x20x20 m $20-40/ton CO 2 for capital charges & maint Amine degradation/environmental impact $1-5/ton CO 2

10 History Repeats CaCO 3 Slurry:::Amine Scrubbing CaCO 3 Event Amine st commercial plant Too commercial for Gov. support Nearly Insurmountable issues Government funds advanced alts Govern. & EPRI fund test facilities MW prototypes MW deployed per regulations First choice dominates 2020

11 Messages on Energy Reversibility is King Greater Capacity reduces Sensible Q Saturation Stripping is more reversible Faster Solvents Enhance Reversibility Greater Heat of Absorption Reduces Energy Greater Stripping T is more reversible Enhanced Stripping is more reversible Energy is approaching 50% of theoretical, a practical limit

12 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Outline 2G/3G Amine scrubbing is available, e.g. PZ at high T Reduced Energy use requires high DH CO2 & large T swing Inefficiency of mechanical compression eliminates membranes, P swing adsorption, and oxycombustion. Competitive cross-exchanger efficiency will be difficult to achieve with solids and viscous liquids. Adequate CO 2 absorption & stripping mass transfer rate is achievable with aqueous amines. Water is significant but manageable. Aqueous amine energy performance will not be beat by advanced capture technologies. 12

13 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Advanced Capture Technologies Claim to Reduce Energy Use Separation Driven by Mechanical Compression Membranes Pressure Swing Adsorption Oxycombustion Separation Driven by Thermal Swing Heat Amine Scrubbing with high T stripping Thermal Swing Adsorption Nonaqueous Solvent Scrubbing 13

14 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Background The MEA 1G Standard Amine scrubbing with absorption/stripping Post-combustion technology 80 years experience in acid gas treating Amine capture processes (Econamine & KS-1) 30 wt % (7 m) MEA benchmark (1 st generation) Fast, high DH abs, good capacity, low m, low cost Not thermally or oxidatively stable 14

15 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Background Concentrated Piperazine (8 m, 40 wt %) Representative 2G/3G amine technology Fastest rate of CO 2 absorption Resistant to oxidation & thermal degradation High-T 2-stage flash process for piperazine Twice the capacity of 7 m MEA Acceptable DH abs = kj/mol Published performance Higher chemical cost, greater viscosity, constrained by solid precipitation 15

16 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis PZ High Temperature 2-Stage Flash Process Flowsheet Absorber 40 C Scrubbed Flue Gas Ldg = 0.31 High Temperature 2-Stage Flash Steam Intercooling Cross-Exchanger T Approach = 5 C Flash Tank 17 bar 150 C Flash Tank 11 bar 150 C Flue Gas Concentrated Piperazine Solvent Ldg =

17 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Overall Energy Analysis of Thermal Swing Regeneration for Amine Scrubbing & Adsorption 1. Energy analysis must consider Regeneration P & T/P value of steam 2. Good Energy Performance requires Greater DH CO2 abs/ads Maximum regeneration T/P Minimum abs/ads T (intercooled) 17

18 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Total Equivalent Work Single-Stage Flash Calculate total equivalent work for generic single-stage flash ΔH CO2 for 60, 70, 80 kj/mol T = 90 to 150 C DH Correlate to DH D [ ] W W total equiv W CO2 equiv 0.75Q flash H2O W T Energy Analysis comp flash 1 T 5 T flash W pump T 5 kj gmol K sink 18

19 Thermal Compression increases Stripper P at greater DH abs &T strip (lower comp work) * P CO strip DH abs 1 1 2, ln * PCO abs R Tabs T 2, strip Thermal Compression reduces heat for water vapor at greater DH abs &T strip (less stripping steam) P H O PH O ( HCO H H O ) EXP PCO PCO R TABS T 2 2 STRIP ABS STRIP

20 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis Maximizing T Swing & DH CO2 Swing Reduces W eq 360 Wtotal(kWh/tonne CO 2 ) 300 DH CO2 =60 kj/mole W total = W equiv +W comp +W pump C Single-stage flash at C Compression to 150 bar Lean P CO2 = 0.5 kpa at 40 C 70 Piperazine 150 C MEA 120 C (DH CO2 -DH H20 )D(1/T) (kj/gmol-k) 80 20

21 W (kwh/tonne CO 2 ) T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Estimated Total Equivalent Work 12% CO 2, 90% Removal, 150 bar, 40 C W equiv 0.75Q T MEA Energy Analysis stm T T stm sink W comp W PZ pump Minimum Work = 109 kwh/tonne CO 2 Separation = 46 kwh/tonne Compression = 63 kwh/tonne Year 21

22 Thermodynamic Efficiency of Common Separation Processes Process Efficiency (%) W minimum / W actual CO 2 Capture by Amine Scrubbing 50 Cryogenic Air Separation 25 Common Distillation Water Desalination by Reverse Osmosis 21 Therefore it is improbable that we will be better than 200 kwh/ton CO 2, with any technology.

23 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Many advanced solvents and sorbents do not have competitive DH CO2 High DH CO2 is difficult to manage in intercooled solid adsorber 23

24 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis Irreversibilities of Two-Stage Flash 22 kwh/tonne CO 2 ABSORBER 40 C 34 kwh/tonne 14 kwh/ tonne 25 kwh/ tonne 9 kwh/tonne 150 C 150 C W IDEAL = 104 kwh/tonne, W REAL = 219 kwh/tonne 24

25 W comp (kj/mol CO 2 ) Multi-stage compressor Reversibility to 150 Bar, 40 o C Intercooling, P/P<2.0, 72% eff MCOMP Work from Aspen Plus Correlation 7 20 atm 0.8 atm ln (150/P in )

26 Compression work, P/P<2 1.9 W comp /W ideal η=0.72, ε=0 η=0.72, ε=0, 2 piece eqn η=0.80, ε= Inlet Pressure (bar)

27 Capture processes driven by mechanical compression are not energy competitive Work (kwh/tonne) Efficiency (%) Minimum Work (Isothermal, ideal compression) PZ with 2-stage regeneration at 150 C Ideal process driven by real compression 72% eff, 40 o C cooling, P j /P j-1 =2 (Ideal Membranes or Pressure Swing Adsorption) Oxycombustion with Ideal air separation Real compressors for Air & CO mol O 2 /mol CO Real Oxycombustion (Darde et al., 2008)

28 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program CROSS-EXCHANGER IRREVERSIBILITY Thermal Swing Regeneration requires Good Cross Exchange Close approach T (5C) High Capacity Low viscosity 28

29 P CO2 (kpa) CO 2 solubility in PZ at 40 o C 4.0 m (Ermatchkov 2006), 3.6 to 8.0 m (This Work) C mol CO 2 /kg"8 m PZ" 0.48 for MEA 1.23 for 2-PE Loading (mol CO 2 /Equiv PZ) 11 th IEA GHG Capture Network Meeting May st,

30 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis Cross-Exchanger Exergy Loss 25 kwh/tonne Steam Make-up for Unrecovered Sensible Heat Loss Q C p DT / capacity ( 3.5 J/mole K)*5K /(0.88 mole/kg) 20 kj/mole CO2 Steam at 155 C W loss 0.75Q T stm T T stm sink *20* kwh/tonne CO 2 1e6 44*

31 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Significance Management Program of viscosity 31

32 Viscosity (cp) Capacity (mol CO2/kg [H2O + PZ] T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program 100 Optimum PZ Concentration 10 Viscosity 1 Capacity N alkalinity (m) 32

33 Capacity/m 0.25 (mol CO2/kg [H2O + amine]/cp 0.25 ) T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Capacity normalized for viscosity PZ MEA 5 m MDEA/5 m PZ N alkalinity (m) 33

34 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Implications for Thermal Swing advanced liquids & solid adsorbents Viscosity should be low Hard to achieve <10-20 cp with advanced liquids Cross-exchange should provide close approach T Hard to achieve 5-10 o C with solid adsorbents CO 2 Working Capacity should must be high >0.7 mol CO 2 /kg sorbent Primary target of materials development Working capacity is Dloading not rich loading 34

35 Mass transfer coefficients CO 2 flux = k ( CO 2 ) CO 2 flux = K G (P CO2,b P CO2 *) P CO2, b Bulk gas P CO2, i [CO 2 ] i Henry s Law: P CO2i = H e * [CO 2 ] i Bulk liquid [CO 2 ] b (=P CO2 *) Gas film Gas-Liquid Interface Liquid film CO 2 flux = k g (P CO2,b - P CO2,i ) = k l ([CO 2 ] i [CO 2 ] b ) = k g (P CO2,i P CO2 *) 35 4/19/2011

36 P CO2,b P CO2,i Bulk Gas [CO 2 ] i Bulk Liquid G-L Interface (P CO2* ) [CO 2 ] b 1 K G Gas Film Reaction Film Diffusion Film 1 k g HCO 2 Ek 0 l P * 1 CO2 0 kl, PROD [CO2] T 1 ' k g 1 K G 1 ' k g fast chemical rxn ' k g Pseudo 1 st order kinetics D CO 2 H k 2 CO [Am] 2 b CO 2 removal = area K G ( P CO2 ) f(area, k g ) Packing Solvent 36 4/19/2011

37 Normalized Flux k g (10-7 mol/s Pa m 2 ) T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis Absorber Reversibility CO 2 Mass Transfer at 40 C (Wetted Wall Column) 20 8 m PZ m MEA % P CO2 40 C (Pa) 5 % 37

38 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis Absorber Exergy Loss 14 kwh/tonne Estimated Packing Area from k g Ln mean k g DP = 2.4e-3 gmol/s-m 2 Lean: k g (P out -P lean *)= 2.2e-6 *( )*10 5 Rich: k g (P in -P rich *) = 5e-7*( )*10 5 Absorber packing volume 1.9e3 m 3 for 800 MW, 250 m 2 /m tonne CO 2 removed/mw-hr 25 x 25 x 13.5 m 1.5 m/s gas velocity Exergy lost/mole CO 2 RTln(P g /P * bulk liq) =RTln(0.12/0.05)= 14 kwh/tonne CO 2 38

39 24 High Temperature Amines Morpholine (Mor), 169 C Piperidine (PD), 164 C Piperazine (PZ), 164 C Hexamethylenediamine (HMDA), 157 C 2-Methylpiperazine (2-MPZ), 152 C 1-Methylpiperazine (1-MPZ), 148 C Pyrrolidine (Pyr), 140 C 2-Amino-2-methyl-1-propanol (AMP), 139 C MDEA in MDEA/PZ Blend, 139 C HomoPZ, 137 C Temp to match MEA deg.( C) Thermal Degradation PZ and its Structural Analogs

40 P CO2 (bar) ΔHabs (kj/mol CO2) T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis 8 m PZ Provides High P at 150 C ºC ΔH abs CO 2 Loading (moles/equiv PZ) 50 19

41 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Do anhydrous solvents reduce Energy? Yes No Condenser Work loss results from water P H2O generates valuable stripper P: Anhydrous solvents/adsorbents generate less P at a given T. Optimized regeneration, e.g. interheated stripping eliminates energy loss from water. Anhydrous solvents/adsorbents pick up water which must be removed anyway. 41

42 T H E U N I V E R S I T Y O F T E X A S A T A U S T I N Luminant Carbon Management Program Energy Analysis Ideal Anhydrous Solvents Reduce Energy Wtotal (kwh/tonne CO 2) DH CO2 60 kj/mole 90 C W total = W equiv +W comp +W pump Single-stage flash at C Compression to 150 bar Lean P CO2 = 0.5 kpa at 40 C 70 Anhydrous Piperazine 150 C MEA 120 C (DH CO2 -DH H20 )D(1/T) (kj/gmol-k) 80 42

43 CO 2 Multistage, Intercooled Compressor Water for reflux <10% H2O Lean Liquid drawoff Stripper Rich

44 Equivalent Work (kj/mol CO 2 ) Stage Flash 0.31 lean loading 8 m PZ 0.40 rich loading 150 C in reboiler(s) 40 2-Stage Flash Simple Stripper Adiabatic Lean Flash Interheated Column Lean Loading (mol CO 2 /mol alk)

45 k g ' avg (x10 7 mol/pa s m 2 ) 10 Two-dimension comparison of solvents 8 6 SarK PZ Derivatives PZ 5/5 MDEA/PZ 2MPZ PZ based solvents MEA 4 2-PE 2 Amino Acids Primary Amine EDA Hindered Amines CO 2 Capacity (mol CO 2 /kg solvent) 45 4/19/2011

46 Fast Solvents Amine (m) Capacity - H CO2 =1.5kPa k g, avg C Deg T ( o C) k 1 = 3e-6 s mol/kg solv kj/mol mol/s Pa m 2 3e-9 s -1 PZ MPZ MDEA/PZ 5/ MPZ/PZ 4/ MDEA/PZ 7/ MPZ HEP MEA

47 Slow Solvents Amine (m) Capacity - H CO2 =1.5kPa k g, avg C Deg T k 1 =3e-9 s -1 mol/kg solv kj/mol mol/s Pa m 2 o C PZ MEA DGA AEP PE MAPA AMP

48 Conclusions Aqueous Amine & Advanced liquid solvents Use solvents with DH CO2 >65 kj/mol Run strippers at max T with thermally stable amines Intercool absorbers to ambient sink Use configurations to recover heat from water vapor Anhydrous solvents lose P benefits of water Maximize solvent capacity/viscosity

49 Conclusions Mechanical compression is not energy competitive Membranes Pressure Swing Adsorption Oxycombustion Thermal Swing Adsorption is no magic bullet Needs DH CO2 > 65 kj/mol with thermally stable materials Must Intercool adsorber Must cross exchange solids to 5 o C approach Needs Dloading >0.7 mol/kg Must maintain efficient mass & heat transfer rates

50 Solvent Management

51 Messages on Solvent Management Thermal Degradation Limits max Stripper T T MEA < T MDEA <T AMP < T PZ Free Radical Autooxidation If fast, in absorber:: if slow, in heat exchanger Alkanolamine > tertiary > Hindered > cyclic(pz) Catalyze by Fe +2, Cu +2, Mn +2 Inhibit by peroxide/radical scavengers, tertiary amine Volatility of amines and degradation products Absorber water wash may work Reduced by hydrophilic groups & speciation Nitrosamines from NO 2 /NO 2- + secondary amine Reclaiming required for coal impurities

52 Where is degradation most likely to occur? Purified Gas 1% CO 2 CO 2 H 2 O (O 2 ) Oxidative Degradation Absorber o C 1 atm Cross Exchanger Stripper 120 o C 1 atm Reboiler Flue Gas 10% CO % O 2 30% MEA a = mm Fe +3 30% MEA a = Thermal Degradation

53 5 Mechanisms for Thermal Degradation 1. Carbamate Polymerization - MEA 2. Cyclic Urea - Ethylenediamine 3. Arm Switching/Elimination - Tertiary Amine 4. SN2 Ring Opening Piperazine 5. Blend Synergism Piperazine/MEA

54 Carbamate Polymerization O NH HO CO 2 - O NH + O - H MEA Carbamate Oxazolidone HO NH 2 + MEA O O NH HO NH HEEDA NH 2 + O O

55 Primary & Secondary Alkanolamines Deg T Amine k 1 = s -1 Structure T ( o C) 2-methyl-aminoethanol 103 Monoethanolamine amino-propanol piperidine ethanol 127 Diglycolamine methyl-2-amino-propanol 137

56 Cyclic urea O NH 2 + O O H 2 N HN NH

57 1 o & 2 o Diamines = cyclic ureas Deg T Amine Structure T ( o C) NH CH Dimethylethylenediamine Diethylenetriamine 105 Methylaminopropanolamine 114 Hydroxyethylethylenediamine 114 Ethylenediamine 121 Hexamethylenediamine 156 H 3 C NH

58 2 Tertiary Quaternary + Secondary HO HO CH 3 N H 3 C CH 3 N + OH OH + HO + HO CH 3 NH + Tertiary 1 + Secondary 2 Tertiary 2 + Secondary 1 Tertiary 1 + Quaternary 2 Tertiary 2 + Quaternary 1 Elimination NH OH OH HO CH 3 N + OH + H 2 O H 3 C HO CH 3 NH + CH 3 + HO OH

59 1-methyl-piperazine o amines 2 o amines + other 3 o amines Amine Structure T ( o C) Dimethylmonoethanolamine 122 CH Tetramethylethylenediamine C N H 3 CH 3 Methyldiethanolamine 128 N-(2-Hydroxyethyl)PZ 132 N,N -Dimethylpiperazine 139 N CH 3 H 3 C N N CH 3

60 Ring Opening HN NH + + HN NH 2 HN NH + N NH 3 Ring Closing N H 2 O OH HN O + H 2 O

61 Cyclic Linear Amine Structure T ( o C) Diglycolamine 133 Homopiperazine 133 Pyrrolidine Methyl-Piperazine 152 Hexamethylenediamine 156 Piperazine HN NH 162 Morpholine 169 NH NH CH 3

62 Interactive Blends Carbamate Polymerization HN NH O NH O HN + N HO NH O Secondary 2 + Tertiary 1 Tertiary 2 + Secondary 1 + HN NH NH + HO OH HN N + NH + 2 HO OH

63 Total Amine Loss in Blends Amine (m) Structure T ( o C) MEA/PZ 104 MEA/AMP AMP/6 PZ MDEA/2 PZ PZ/4 2MPZ PZ/3.9 1MPZ/ DMPZ 160

64 Oxidation

65 Amine Oxidation (mol/mol CO 2 ) O 2 solubility & Mass Transfer 6.E-5 PZ MDEA MEA 4.E-5 Total 2.E-5 Exchanger Absorber Sump 0.E+0 2.E-04 Oxygen 2.E-03 Rate Constant (s -1 ) 2.E-02

66 Fraction of Initial Amine Avoid Oxidation with PZ or Inh A m PZ m MEA 7 m MEA mm Inhibitor A Oxidation Conditions: 55 C, 1400 rpm 98% O 2 / 2% CO mm Fe mm Cr mm Ni Experiment Time (hrs)

67 Inhibition (% NH3 rate) Inhibitors in MEA at 70 C, 98kPa air, 2kPa CO 2 100% 80% 60% 40% DP DA HP Citric acid HP+DA IA + HP IA EDTA MDEA 20% 0% Inhibitor (wt%)

68 Autoxidation of MEA Initiation Propagation Termination Inhibition MEAOOH + Fe +2 MEAO + Fe +3 MEAOOH + Fe +3 MEAOO + Fe +2 MEAO + MEA MEAOH + MEA MEAOO + MEA MEAOOH + MEA MEA + O 2 MEA-OO R + R mol. Prod. R + Inh RH + Inh MEAOOH + Inh MEAOH + InhO

69 NH3 Rate (mmol/kg/hr) m MEA with transition metals Conditions: 70 C, 98kPa air, 2kPa CO 2 1 mm Cu 2+ 1 mm Mn 2+ 1 mm Fe 2+ Mild effect: V, Cr No significant effect: Ti, Mo, Co, Ni, Sn, Se, Ce, Zn Time (hrs)

70 NH3 Rate (mmol/kg/hr) m pilot plant MEA with HEDP 70 C, 98kPa O 2, 2kPa CO 2, 0.5mM Fe HEDP to 1.5 wt% H 3 HO O P C HO OH O P OH OH wt% DTPA NH3 rate stable for >48hrs Time (hrs) O HO OH N O N O N OH O O OH OH

71 Environmental Impact of Degradation Products Volatile Products Require water wash Nonvolatile products Require Reclaiming

72 Some Oxidation Products of MEA Product Structure Ammonia (V) NH 3 Formaldehyde (V, NV) H 2 CO Formate (NV) Eide-Haugmo N-(2-hydroxyethyl)-formamide (V) O HCOO- NH OH N-hydroxyethyl-imidazole (V) N-(2-hydroxyethyl)-2-[(2-hydroxyethyl) amino] acetamide (NV)

73 7 m MDEA/2 m PZ Oxidized at 120 o C Products (CO 2 carrying) C-Loss (%) Diethanolamine/Methylaminoethanol 40 1-methyl PZ 8.4 1,4-Dimethyl PZ 0.9 Aminoethyl PZ 3.5 N-formyl PZ (amide) 8.3 Formate & other acids 2.5 Bicine 5.3 Hydroxyethyl sarcosine 10.5 ~79.5

74 PZ thermal products, 165 o C Product Structure N loss (%) N-Formyl PZ (V) 32 NH 3 (V) 14 Aminoethylpiperazine (NV) 2-Imidazolidone (V) 6 HN HN N N O O NH 2 NH 3 H N 10 Hydroxyethylpiperazine (NV) HN N OH N H 4

75 HO Degradation of 5 M MEA 120 o C, 0.4 mol CO 2 /mol MEA NH 2 O HN N OH HO NH NH 2 O HN N NH OH HO NH NH NH 2

76 Volatility Issues Amine volatility In H 2 O In loaded solution As a methylated degradation product, e.g. 1.4 dimethylpiperazine, methylamine Oxidation products HEI Formamide Ammonia Nitrosamine from sec amine and NO 2 /NO 2 -

77 Amine Volatility (Pa) at 40 o C Amine Ldg = 0 Ldg: P CO2 = o C 5m MDEA/5m PZ 0.17/ /0.51 7m MDEA/2m PZ 0.56/ /0.21 8m PZ (8.8) m EDA m MEA m AMP

78 Nitrosamine Characteristics Organic compounds containing -N-N=O Secondary amine reacts with nitrosating agent Nitrous acid in acidic conditions In Vivo Nitrite in basic conditions for amine scrubbing

79

80 Normalized MNPZ (mol MNPZ/mol NO 2i model ) MNPZ and Decomposition at High Temperatures C 150C 50 mm NO2 150C 15 mm NO2 135C Time (Day)

81 Aerosols

82 Message on Thermal Degradation Stripper energy is constrained by the max T permitted by Degradation Linear alkanolamines and diamines degrade by polymerization & urea formation at o C Tertiary amines degrade by arm switching & elimination at o C Piperazine and related cyclic amines degrade by ring opening at o C.

83 Message on Oxidation As amines become more resistant, oxidation shifts from the absorber to the heat exchanger MEA & alkanolamines readily oxidize in the absorber unless inhibited by radical or peroxide scavengers Tertiary amines inhibit self oxidation, probably by scavenging peroxides Piperazine oxidizes only at the higher T of the heat exchanger exit

84 Message on Environmental Impact Amine degradation must be minimized to manage secondary environmental impact. Volatile Products can leave with flue gas Aldehydes, formate, ammonia, volatile amines, amides Nonvolatile products make up reclaimer waste Polyamines, Cyclic urea, amino acids

85 Conclusions Amine Scrubbing can be Deployed by 2019 Improved Amine Solvents and Processes Reduce Energy from 400% to 200% of Minimum W Provide Stable, Benign Solvents Simplify systems to reduce capital Cost As Limestone Slurry Rules FGD after 30 yrs; Amine Scrubbing will dominate CO 2 capture. Other technologies are unlikely to compete for Post-combustion capture.