Amino Acid Solvents. Le Li, Gary Rochelle. University of Texas at Austin Luminant Carbon Management Program

Transcription

1 Amino Acid Solvents 1st Post Combustion Capture Conference Abu Dhabi, United Arab Emirates. May 18 th, 2011 Le Li, Gary Rochelle University of Texas at Austin Luminant Carbon Management Program

2 Overview Introduction Amino Acid Solvents Experimental Methods Data Analysis Experimental Results K+ based solvents Rate CO 2 solubility Heat of Absorption Na+ based solvent Summary Conclusions Amino Acid Solvents for Natural Gas Application 1 5/18/2011

3 Introduction - Amino Acid Solvents

4 Amino Acid Solvents Intrinsic Characteristics Nonvolatile Biodegradable Low Environmental Impact Stable for oxidative degradation* Precipitation with CO 2 loading Activate amino group for reaction with CO 2 with equi-molar base (KOH, NaOH) Activated amino group react with CO 2 same as amines Amino Carboxylic Acid Amino Sulfonic Acid * Rochelle Group, 3 rd Quarterly Report 2010, Alex Voice 3 5/18/2011

5 Amino acid Structure MW Solubility Previous Work Glycine 75 Sarcosine 89 Taurine 125 6m, P* CO2 = 0.5kPa 6m with CO 2 loading 5m, P* CO2 = 0.05 kpa reaction rate/kinetics, CO 2 solubility, physical parameter physical parameters, CO 2 solubility reaction rate/kinetics, CO 2 solubility, physical parameter Homo - taurine 139 6m with CO 2 loading N/A β - Alanine m P* CO2 =6kPa physical parameters, Solid solubility Proline 115 Soluble at 8m WWC rate and solubility, physical parameters 4 5/18/2011

6 Introduction - Experimental Methods

7 WWC Set Up CO 2 flux k g P CO2 * 6 5/18/2011

8 Data Analysis Rate (k g ) N = 1 K k co g = 1 k g K ( P 2 G l 1 + k g ' P co2, g CO2, ' f 2 2 g = Directly Measured ( k2, HCO, DCO,[ Am] i, etc) CO 2 Solubility (P CO2* ): function of T and loading (α) * 2 ln( P CO ) = a + b / T + c α + d α / T + e α 2 Heat of Absorption: function of loading (α) only d ln P H Abs = R d(1/ T ) Calculate: k g avg and cyclic capacity * ) = R N CO2 = k l ([CO 2 ] i -[CO 2 ] b ) = k g (P co2i P CO2* ) ( b + d α ) 7 5/18/2011

9 Operation Lean & Rich Loadings P CO2 =1.2kPa 1.2% CO 1 atm 90% Removal Solvent P CO2 * α lean Cyclic Capacity = mol CO 2 /kg solution = α ( mol Alk / kgsolution) k g avg = ( P CO Flux 2, gas CO 2 P, LM * CO 2 ) LM 12% CO 1 atm P CO2 =12kPa Coal Flue Gas α P CO2 * = 5kPa 8 5/18/2011

10 Flue gas change = loadings change Coal Fired Plants GT Natural Gas Absorber (@ 1atm) Flue Gas P CO2 (kpa) P CO2 40 C (kpa) Flue Gas P CO2 (kpa) P CO2 C (kpa) Bottom (rich) Top (lean) α = α PCO 2 = 5kPa α PCO 2 = 0. 5kPa α = α PCO 2 = 1kPa α PCO 2 = 0. 1kPa 9 5/18/2011

11 Experimental Results: K+ based solvents

12 Absorption Rates for 6.5m beta-alak 1.E-05 k ' g D 40 C CO 2 H k 2 CO [Am] 2 b NATURAL GAS COAL 8m 40 C k g ' (mol/s Pa m 2 ) 1.E C 100 C 80 C 7m 40 C 1.E P* 40 C (Pa) 11 5/18/2011

13 CO 2 Solubility of 6.5m beta AlaK m 100 C 7m MEA 40 C P* CO2 (kpa) C 80 C 60 C 40 C CO 2 loading (mol CO 2 /mol Alk) 5/18/2011

14 Solvent Capacity for 6.5m beta AlaK Capacity = α ( mol Alk / kgsolution) MEA Capacity = 0.5 mol CO 2 /mol alk 7m MEA 40 C 5 kpa P* CO2 (kpa) kpa C Gas Capacity 0.28 mol CO 2 /mol alk Coal Capacity 0.25 mol CO 2 /mol alk CO 2 loading (mol CO 2 /mol Alk) 5/18/2011

15 Heat of Absorption H abs 7m MEA 80 P* CO2 (kpa) H abs β-alak 100 C 80 C 60 C d ln P H Abs = R d(1/ T ) 2 40 C ln( P) = a + b / T + c α + d α / T + e α = R ( b + d α ) CO 2 loading (mol CO 2 /mol alk) 14 5/18/ H abs (kj/mol)

16 Summary of Results Amino Acid (m) CO 2 Capacity (mol CO 2 /kg Solution) k g avg (@40 C) (x 10-7 mol CO 2 /s Pa m 2 ) P CO2 =1.5kPa Mid H abs (kj/mol) P CO2 =0.5kPa Coal Gas Coal Gas Coal Gas GlyK (3.55) GlyK (6) 0.35* * * ~ 50% 7m MEA SarK (6) Tau/Htau (3/5) 0.2* * 10 75* 80 β AlaK (6.5) 0.25* * 7 64* 67 MEA (7m, Dugas) X3 15 5/18/

17 Experimental Results: Na+ Solvent

18 4.5m SarNa Amino Acid (m) CO 2 Capacity (mol CO 2 /kg Solution) k g avg (@40 C) (x 10-7 mol CO 2 /s Pa m 2 ) P CO2 =1.5kPa Mid H abs (kj/mol) P CO2 =0.5kPa Coal Gas Coal Gas Coal Gas GlyK (3.55) GlyK (6) 0.35* * * 69 SarK (6) Tau/Htau (3/5) 0.2* * 10 75* 80 β AlaK (6.5) 0.25* * * 67 MEA (7m, Dugas) /18/2011

19 CO 2 Solubility of Sarcosine C H 3 NH O O P CO2 * (kpa) C 80 C 60 C 40 C 100 C Empty Square: SarK (Arnu NTNU) Filled Square: 6 m SarK (WWC) Asterisk (*): 4.5 m SarNa (WWC) CO 2 Loading (mol CO 2 /mol alk) 5/18/2011

20 C H 3 NH O Result 4.5m SarNa O - Property Operation condition SarNa 4.5 m SarK 6 m MEA 7 m (Dugas, 2009) k g ' avg ( 10 7 mol/s Pa m 2 ) Capacity (mol CO 2 /kg solvent) H abs (kj/mol) Coal 4.5* Gas Coal 0.31* Gas Coal (@P* CO2 =1500) Gas (@P* CO2 =500) 54* /18/2011

21 Rate vs. Capacity (Coal) k g ' 40 C (x10 7 mol/pa s m 2 ) Capacity = α ( mol Alk / kgsolution) Amino Acids SarK MEA Primary Amine PZ based solvents PZ Derivative 5/5 MDEA/PZ CO 2 Capacity (mol CO 2 /kg solvent) PZ EDA 2MPZ 2-PE Hindered Amines 20 5/18/2011

22 Limitations Intrinsic low capacity mol CO 2 /kg solvent (50% 7m MEA) Capacity = α ( mol Alk / kgsolution) Solubility limits alkalinity in solution Base (Na+ / K+)increase solvent mass kg solution = (amino acid + H 2 O + base + ) Precipitation at rich loadings 21 5/18/2011

23 Amino Acids for Natural Gas Applications

24 Solvent Criteria for Natural Gas (vs. Coal) Lower CO 2 content (Gas: 3 vol%, Coal: 12%) Operate at leaner loading regions Amino Acids Advantage, Amines Advantage Higher O 2 content (Gas:15 vol%, Coal: 8%) Effect of oxidative degradation more important (12X) Amino Acids?, Amines? Higher total gas rate (Gas = 2 X Coal) Solvent volatility more important, capacity less important Amino Acids Advantage, Amines Disadvantage Low Environmental Impact Amino Acids Advantage, Amines Disadvantage 23 5/18/2011

25 Conclusions

26 6m SarK has competitive rates against 7m MEA K + salt of amino acids are more soluble than Na + salt Base choice (K + /Na + ) does not change CO 2 solubility Two limitations of amino acid solvents Low capacity (~50% 7m MEA) Rich loading solid precipitations Amino acids not competitive at coal conditions 25 Low rates Low heat of absorption Except: Tau/Htau blend Environmental advantage Appropriate for natural gas applications 5/18/2011

27 Thank You! 26 5/18/2011

28 Neutralization Activate amino group for reaction with CO 2 with equimolar base (KOH, NaOH, K 2 CO 3, etc) NH 3+ R COO - + KOH NH 2 R COO - K + + H 2 O Activated amino group react with CO 2 like amines 27 5/18/2011

29 Reactions with CO 2 Deprotonated amino acids behave like amines Primary / Secondary amino acid Carbamate formation k f k r + B-H Tertiary amino acid (Termolecular Mechanism) [AminoAcid] + [CO 2 ] + [H 2 O] [AminoAcid + ] + [HCO 3- ] Bicarbonate formation 28 5/18/2011

30 Rate (k g ) for Amino Acids (K + ) at 40 C k g 40 C (mol/s Pa m 2 ) 1.00E E E-07 MEA 7m ' k g D CO TauK 5m 2 H k β AlaK 6.5m 2 CO [Am] 2 SarK 6m b NATURAL GAS ProK 8m COAL 8m PZ GlyK 3.55m Tau/HtauK 3/5m P* 40 C (Pa) 29 5/18/2011

31 Heat of Absorption (coal range) 30 5/18/2011

32 C H 3 NH O Rates of 4.5 m SarNa 1.E-05 O - k g ' (mol/s Pa m 2 ) 1.E C 80 C 40 C 100 C 6 m 40 C 8m 40 C 7m 40 C 1.E P 40 C (Pa) 31 5/18/2011

33 Natural Gas Flue Gas Properties CH % Excess 21% O 2 79% N 2 Flue Gas Rate (400MW) Natural Gas Coal 2.5 x 10 6 m 3 /hr 1.5 x 10 6 m 3 /hr CO 2 3% 12% O 2 15% 5-8% 32 5/18/2011