Carbon Dioxide Absorption/Stripping Modeling

Transcription

1 Carbon Dioxide Absorption/Stripping Modeling Jorge M. Plaza Luminant Carbon Management Program Department of Chemical Engineering The University of Texas at Austin Joint Seminar on CO 2 Absorption Fundamentals NTNU, Trondheim, June 15, 2009

2 Outline Mass Transfer Area of Structured Packing Stripper Modeling Pilot Plant Analysis Pilot Plant Campaign Fall 09 6/15/2009 The University of Texas at Austin 2

3 Mass Transfer Area of Structured Packing Robert Tsai 6/15/2009 The University of Texas at Austin 3

4 Packed Column Setup Air Outlet ( ppm CO 2 ) Demister / Liquid Distributor Blower (Air: ppm CO 2 ) dp Packing ~ 3 m (10 ft ) PVC: ID ~ 427 mm (16.8 ) 180, 300, 450 ACFM (0.6, 1.0, 1.5 m/s) Storage Tank Pump (up to 75 m 3 /m 2 -h or 30 gpm/ft 2 ) 6/15/2009 The University of Texas at Austin 4

5 Packing Area Characterization (Series resistance) 1 K G = 1 k G + k 1 ' g k g = Flux = (P 0) k OH [OH H CO2,i CO 2 ]D CO 2,L [1] 1/k G << 1/k g for high gas velocity, dilute NaOH K G k g K G a e = U G y ln y ZRT CO CO 2 2 in out a e U G yco ln yco2 Zk RT g 2 in out Physical properties μ L : PEO / σ: Tergitol NP-7 (Kinetics (k g ) verified with WWC) [1] Pohorecki, R.; Moniuk, W. Kinetics of reaction between carbon dioxide and hydroxyl ions in aqueous electrolyte solutions. Chem. Eng. Sci. 1988, 43 (7), /15/2009 The University of Texas at Austin 5

6 M250Y/250X: Mass Transfer Areas 6/15/2009 The University of Texas at Austin 6

7 M250Y/M250X: 10 gpm/ft 2 ΔP dry,m250y Z = 0.055F /15/2009 The University of Texas at Austin 7

8 ρ L g σ 1 3 Q L p 4 3 6/15/2009 The University of Texas at Austin 8

9 Geometry Conclusions on Mass Transfer Area No effect of corrugation angle (45 vs. 60 ) X (60 ) superior to Y (45 ) for CO 2 absorption Same area and less pressure drop Fluid properties No effect of liquid viscosity Weak effect of surface tension (greatest for 500- series) Database represented well (±15%) by global correlation: ae = ( We )( Fr ) a p [ ] 116 6/15/2009 The University of Texas at Austin 9 L L

10 ρ L g σ 1 3 Q L p 4 3 6/15/2009 The University of Texas at Austin 10

11 Comparison with Literature 45 / 60 B1-250 / B [2] M250Y / M250X (Tsai) ΔP / ΔP F G,lp / F G,lp HETP / HETP (analogous to k G a e ) a e / a e --- ~1 k G / k G [3] [2] Olujic, Z.; Seibert, A.F.; Fair, J.R. Influence of corrugation geometry on the performance of structured packings: an experimental study. Chem Eng. Process. 2000, 39 (4) 335. [3] Rocha, J.A.; Bravo, J.L.; Fair, J.R. Distillation columns containing structured packings: a comprehensive model for their performance. 2. Masstransfer model. Ind. Eng. Chem. Res. 1996, 35 (5), /15/2009 The University of Texas at Austin 11

12 Stripper Modeling David Van Wagener 6/15/2009 The University of Texas at Austin 12

13 Simple Stripper 6/15/2009 The University of Texas at Austin 13

14 Simple Stripper Regression of Hilliard (2008) was rerun with available high concentration and high temperature data sets A simple stripper was modeled and compared against the base case (7 m MEA) Aspen Plus RateSep TM Heat and mass transfer calculations Equilibrium reactions Fixed rich P* CO2 (ldg) specific to each solvent 160 kpa column pressure 5 C cold side approach on cross exchanger Final compression to 15 MPa 6/15/2009 The University of Texas at Austin 14

15 Multi-Stage Flash 6/15/2009 The University of Texas at Austin 15

16 Multistage Flash High-temperature multistage flash H 2 O properties from DIPPR Modeled with correlations for PZ properties Equilibrium CO 2 partial pressure ldg ln P * CO ldg 2 RT T Heat capacity C p 2 ( Pa) = ldg kj = ωh kg K 2 O C 3 2 ( T ) + ( T ) p, H O + ωpz 2 ω 2 CO2 Heat of vaporization for CO 2 and H 2 O from Gibbs- Helmholtz Established correlation for compression to 15 MPa Minimum number of stages to have maximum pressure ratio of 2 6/15/2009 The University of Texas at Austin 16

17 Compression Work from Aspen W comp = ln Pin 6/15/2009 The University of Texas at Austin 17

18 Lean Loading Optimization T + 10K T = W 10 reb sink W eq Qreb pump / comp Treb + K 6/15/2009 The University of Texas at Austin 18

19 8 m PZ Heat Capacity 6/15/2009 The University of Texas at Austin 19

20 Pilot Plant Analysis Jorge M. Plaza David Van Wagener 6/15/2009 The University of Texas at Austin 20

21 CO 2 Pilot Plant Pickle Research Center Multi-use facility (distillation/extraction) Column ID = 0.43 m (16.8 in) Packed height 6.1 m in 2 beds (3 m each) Collector plate & redistributor between packed beds 3-6 tons CO 2 /day Equiv to MW 6/15/2009 The University of Texas at Austin 21

22 8 m PZ Pilot Plant Flowsheet Recycled CO 2 Absorber Gas Acc 52-93% Removal Gas Out gpm Liq Acc Condenser Cross Exchanger psia Stripper 350 acfm Air 12% CO 2 Blower CO 2 Makeup Feed Tank Trim Cooler Rich Amine Lean Amine 1450 Btu/ lb CO 2 6/15/2009 The University of Texas at Austin 22

23 Conditions Campaign in November m, 8m and 9 m PZ Packing Absorber: Mellapak 2X Stripper: IMTP-40 Inlet gas : 10% - 12 % CO 2 Liquid volume : m 3 /m 2 -s 6/15/2009 The University of Texas at Austin 23

24 Overall gas side mass transfer coefficient Effective packing area (a eff ) from Tsai: Log Mean Pressure Difference LMPD 6/15/2009 The University of Texas at Austin 24

25 Wetted wall kg and pilot plant K G 5m PZ 5m PZ 40 o C (Dugas) 9m PZ 8m PZ 7.5m PZ 5m PZ 5m PZ 60 o C (Dugas) 6.4m K + /1.6 m PZ (Chen, 2007) 9 m MEA (Plaza, 2008) 7m MEA (Dugas, 2006) 5m K + /2.5m PZ (Chen, 2007) 6/15/2009 The University of Texas at Austin 25

26 Wetted wall kg and Pilot plant K G 8m PZ 9m PZ 8m PZ 8m PZ 40 o C (Dugas) 7.5m PZ 5m PZ 8m PZ 60 o C (Dugas) 6.4m K + /1.6 m PZ (Chen, 2007) 7m MEA (Dugas, 2006) 5m K + /2.5m PZ (Chen, 2007) 9 m MEA (Plaza, 2008) 6/15/2009 The University of Texas at Austin 26

27 Stripper Performance *Yokoyama T Japanese R&D on Large-Scale CO2 Capture ECI Conference on Separations Technology VI: New Perspectives on Very Large- Scale Operations. Fraser Island, Queensland, Australia 6/15/2009 The University of Texas at Austin 27

28 Conclusions Pilot plant K g data is consistent with WWC data 5 m PZ exhibits the highest values for K g 5 times higher than 7 m MEA 4 times higher than 5 m K + /2.5 m PZ 20% higher than 8m PZ but has less capacity PZ shows lower heat requirements 20% less than 9m MEA Comparable performance to KS-1 6/15/2009 The University of Texas at Austin 28

29 Pilot Plant Campaign Fall 09 Eric Chen 6/15/2009 The University of Texas at Austin 29

30 Motivation for 8 m PZ 2-Stage Flash UT Pilot Plant Test Build on success of 8 m PZ pilot plant Test two-stage flash concept Coupled with absorber intercooling Demonstrate process concept, operability and energy reduction Field Pilot Test Extended field demonstration (6-12 months) Demonstrate solvent robustness with real flue gas 6/15/2009 The University of Texas at Austin 30

31 Absorber-Side Process Concept Gas Out Intercooling Feedtank Solvent Cooler CO2 Recycle Cross-Exchanger Hot side Cross-Exchange CO2 Makeup Cold Side Cross-Exchange 6/15/2009 The University of Texas at Austin 31

32 Stripper-Side Process Concept CO2 Recycle Flash Tank 13.5 atm 150 C Flash Tank 8 atm 150 C Overhead CO 2 Accumulator Liquid Accumulator Bypass to Feedtank To Feedtank Steam Heater To Feedtank From Absorber HP Pump HP Cross Exchanger Two-stage Flash 6/15/2009 The University of Texas at Austin 32

33 Advanced Process Flowsheet Gas Out CO 2 Accumulator Absorber Two-stage Flash Intercooling Absorber Feedtank Flash Tank 13.5 atm 150 C Flash Tank 8 atm 150 C Solvent Cooler Steam Heater Liquid Accumulator CO2 Makeup HP Pump HP Cross Exchanger 6/15/2009 The University of Texas at Austin 33

34 Pilot Plant Process Design Two-stage flash unit designed to tie into field test unit Skid mounted equipment sized for 15 gpm and 350 acfm High pressure pump (multi-stage centrifugal) Cross-exchanger (flashing above 130 C) 2 steam heaters (flashing) 2 flash drums (1 min residence time) Instrumentation, control valves, flowmeter Possible Emerson wireless instrument donation for skid Absorber intercooling (non-portable) Use original Alfa Laval M6 plate and frame exchanger Rebuild existing P-105 pump Flow measurement and temperature control 6/15/2009 The University of Texas at Austin 34

35 Questions? Jorge M. Plaza 6/15/2009 The University of Texas at Austin 35