Performance of Aqueous MDEA Blends for CO 2 Removal from Flue Gases

Transcription

1 Performance of Aqueous MDEA Blends for CO 2 Removal from Flue Gases P.J.G. Huttenhuis, E.P. van Elk, G.F. Versteeg Procede Group B.V., The Netherlands 10 th MEETING of the INTERNATIONAL POST- COMBUSTION CO 2 CAPTURE NETWORK 24 May 2007, Lyon, France

2 Content Introduction; Rate based model; Results; Conclusions & Future work. Acknowledgement capture meeting; IFP; Lyon 24 May

3 Introduction Experience with Post Combustion CO 2 capture : - Fluor Econamine process (30 wt.% MEA); - Kerr-McGee / ABB Lummus Crest process (15-20 wt. % MEA). Major challenges are: required scale and capture costs: CAPACITY [tonne CO 2 /hr] CAPTURE COSTS [ /tonne CO 2 ] Current Goal Current Goal ) ) 500 MW Coal fired plant capture meeting; IFP; Lyon 24 May

4 Introduction Typical flowsheet: Treated Gas ACID GAS COOLER acid gas LEAN SOLVENT COOLER Lean solvent Make Up Water REFLUX DRUM ABSORBER Flash Gas REGENERATOR Feed Gas REBOILER Steam Rich solvent FLASH DRUM Optional Condensate capture meeting; IFP; Lyon 24 May

5 Introduction Main problems with this technology are: - Degradation due to the presence of oxygen; - Corrosion; - High absorber costs; - High regeneration costs; ± 70 % of operational costs (4 GJ / tonne CO 2 ). Better Solvents required capture meeting; IFP; Lyon 24 May

6 Introduction New solvent developments by several research programs: - KS-1 : low regeneration energy (MHI); - Amino acids: low volatility (TNO and Univeristy of Twente); - K 2 CO 3 activated with PZ: low volatilty and no degradation (University of Texas); - Mixed amines (MEA : MDEA; 4 : 1); lower regeneration energy (University of Regina). This work: study of performance of aqueous MDEA activated with different accelerators (primary and secondary amines) in the absorber. capture meeting; IFP; Lyon 24 May

7 Introduction MEA (primary amine) versus MDEA (tertiary amine): MEA MDEA Stoichiometry (amine-co 2 ) 2:1 1:1 Heat of absorption [MJ/kg CO 2 ] Reaction rate 298 K [m 3.mol -1.s -1 ] Volatility [P amine in 373 K] Corrosion rate [mili-inch/year] capture meeting; IFP; Lyon 24 May

8 Rate Based Model - Tray to tray procedure (Blauwhof 1985); - Series of ideal CISTR s; - No pressure drop and back mixing; - Constant heat and mass transfer parameters (k l, k g, a, h l, C p ); - Physical parameters only function of temperature (ρ, µ, D, K, m); - limited to blend of two amines; - ideal vapour / liquid phase (fugacity = 1). capture meeting; IFP; Lyon 24 May

9 Rate Based Model Process design: Hydrodynamics; Mass transfer parameters; Kinetics (enhancement); VLE (physical and chemical). Flux according film model: capture meeting; IFP; Lyon 24 May

10 Rate Based Model Involved chemical reactions: all amine systems: 2H 2 O H 3 O + + OH - CO H 2 O HCO 3- + H 3 O + HCO 3- + H 2 O CO H 3 O + R 1 R 2 R 3 N + H 2 O R 1 R 2 R 3 H + +OH - (water ionization) (bicarbonate formation) (carbonate formation) (amine protonation) for primary / secondary amines only ( if R 1 and/or R 2 is a hydrogen atom): 2R 2 R 3 NH + CO 2 R 2 R 3 NCOO - + R 2 R 3 NH + 2 (carbamate formation) capture meeting; IFP; Lyon 24 May

11 Rate Based Model CO 2 Solubility CO 2 partial pressure [kpa] CO 2 loading [mol/mol] 4.3 M MDEA - Austgen M MDEA - Huang MDEA + 2 M /MEA - Austgen M MEA - Lee M MEA - Shen 1992 capture meeting; IFP; Lyon 24 May

12 Results Input data for absorber simulations: Flue gas flow is 500 Nm 3 /s with 12 % CO 2 (typical coal fired); 90 % CO 2 removal; Absorber temperature is 40 C; K g is and k l is m/s; 3 M aqueous amine (> 90 % MDEA + make up accelerator); Simulated accelerators: MEA; DGA (primary) and DEA, MMEA, DIPA (secondary). HO N MDEA OH HO O DGA NH 2 HO MMEA H N HO MEA NH 2 HO N H DEA OH OH N H DIPA OH capture meeting; IFP; Lyon 24 May

13 Results Influence number of trays on column length: Column length [m] number of trays [-] Minimum number of calculated trays should be at least 30 to assure plugflow in the column. capture meeting; IFP; Lyon 24 May

14 Results Influence type of accelerator (5 mole %) on column length: no acc. 60 DIPA Column Length [m] DEA DGA MMEA MEA capture meeting; IFP; Lyon 24 May

15 Results Influence amount of accelerator on column length: Column Length [m] DIPA DEA DGA MMEA MEA 0 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% concentration accelerator [mol %] capture meeting; IFP; Lyon 24 May

16 Results Influence MEA concentration on calculated enhancement: 10 Enhancement [-] % MEA 0.5 % MEA 1 % MEA 2 % MEA 5 % MEA 10 % MEA E E E E E E+04 P CO2 [Pa] capture meeting; IFP; Lyon 24 May

17 Results Speciation in 3 M amine (resp. 1 % and 10 % MEA): 1.0E E E E-01 Molefraction [-] 1.0E-02 Molefraction [-] 1.0E E E-03 MDEA MDEAH+ MEA MEAH+ MEACOO- HCO3- CO E Column heigth [m] MDEA MDEAH+ MEA MEAH+ MEACOO- HCO3- CO E Column heigth [m] [MEA] 1 % 10% Liquid flow [m 3 /s] Rich loading [mole CO 2 /mole amine] capture meeting; IFP; Lyon 24 May

18 Conclusions & Future work MEA seems a very good accelerator; Small amount of MEA added to an aqueous MDEA blend results in a significant shorter column; Aqueous blends of MDEA/MEA may be competitive with aqueous MEA (lower regeneration, less corrosion, better stoichiometry); Model can provide good insight in solvent behavior in the absorber. capture meeting; IFP; Lyon 24 May

19 Conclusions & Future work - Study influence of tertiary amine type on absorption performance; - Incorporation of desorber and other unit operations to study regeneration energy; - Extension to more accurate thermodynamic models, like E-EOS models. capture meeting; IFP; Lyon 24 May

20 Acknowledgement - This work has been carried out as part of the CAPTECH project; - CAPTECH is sponsored by the Dutch Ministry of Economic Affairs and is part of the EOS Long Term (Energy Research Strategy) research program. capture meeting; IFP; Lyon 24 May

21 Thank you! capture meeting; IFP; Lyon 24 May