Solvent Development for Aqueous Absorption/Stripping of CO 2. The University of Texas at Austin J. Tim Cullinane and Gary T. Rochelle April 27, 2004

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1 Solvent Development for Aqueous Absorption/Stripping of 2 The University of Texas at Austin J. Tim ullinane and Gary T. Rochelle April 27, 2004

2 utline verview Process onsiderations Solvent Development Experimental Methods Development of Aqueous K + /PZ ther UT Research Activities Degradation Process Modeling Pilot Plant/Packing Selection onclusions

3 U.S. 2 Emissions from Fossil Fuel ombustion by Sector ommercial 4.8% Industrial 31.8% Power Plant - oal 47.1% Residential 9.7% Power Plant - Petroleum 2.0% Power Plant - atural Gas 4.6% Total U.S. Emissions = Tg 2 Eq. Excludes Transportation, EPA (1999)

4 Advantages of Aqueous Absorption/Stripping ear ommercial Technology Process used for treating H 2 & natural gas MEA demonstrated on small coal plants Promoted K 2 3 used for H 2 treating Post-process Technology Development Lower cost and less risk to process Resolve problems in small pilot plants Demo Full-scale absorbers with 100 MW gas Problems 20-40% energy use High capital cost

5 Enhancing 2 apture by Amines 1. ontactor Development Packing 2. Process Flowsheet Innovations Multi-pressure stripper Inter-cooling 3. Energy Integration Power plant specific 4. Engineering Development Large-scale equipment 5. Solvent Development

6 2 apture by Amines Sweet Gas 1% 2 P 2 * ~ 300 Pa ooler 2-4 mol H 2 /mol 2 Absorber T = o Stripper T = o P 2 * ~ 3000 Pa Sour Gas 10% 2 Rich Amine Lean Amine Reboiler H = kcal/mol 2

7 Solvent Development K + /PZ 1. Thermodynamics 2. Rates of Absorption 3. Degradation 4. System Modeling 5. Pilot Plant Bench-Scale Work Fundamental Process Flowsheet Large-Scale Work

8 H H H + H H H H H H H H + H H H H 2 Absorption by K + /Piperazine arbonate Species Piperazine Species 2 +

9 PZ Speciation by 1 H MR H 2 H 2 H 2 H2 H 2 H 2 H H 2 H2 H 2 H 2 H H H 2 H2 H 2 H 2 H H 2 H2

10 Wetted-Wall olumn Pressure ontrol (35 60 psig) WW (38 cm 2 ) ondenser Sample Port IR 2 Analyzer Pump (2 4 cm 3 /s) 2 2 Saturator ( o ) Heater ( o ) Solution Reservoir (1000 cm 3 ) Flow ontrollers (4 6 L/min)

11 Fundamental Equilibrium Modeling Uses Electrolyte RTL Model Rigorous activity coefficient model Benefits Versatile can be used for broad range of conditions, systems Develops/supported by theory more accurate extrapolations Predicts complicated behavior hallenges Accurate representation of entire system Meaningful results can require a lot of data Thermodynamic consistency

12 Model Parameter Summary System Data Types Parameters Data Points K 2 3, H 2 Boiling pt. elev., P H2 * KH 3, K 2 3, H 2 P 2 * PZ, H 2 UIFA 4 21 PZ, 2, H 2 MR, P 2 * 3 a 406 PZ, K +, 2, H 2 MR, P 2 * a. 6 parameters for equilibrium constants also regressed

13 Speciation in 1.8 m PZ at 60 o ~300 Pa ~10000 Pa 0.8 PZ Fraction of Total PZ Total Reactive Species PZH + H + PZ PZ - PZ( - ) Loading (mol 2 /mol PZ)

14 Speciation in 5.0 m K + /2.5 m PZ at 60 o PZ ~300 Pa ~10000 Pa Fraction of Total PZ PZ - Total Reactive Species PZ( - ) 2 H + PZ - PZH Loading (mol 2 /(mol K + + mol PZ)

15 Equilibrium in K + /PZ at 60 o 3.6 m K + /1.8 m PZ 5.0 m K + /2.5 m PZ 6.2 m K + /1.2 m PZ 3.6 m K + /0.6 m PZ 1.8 m PZ 7 m (30wt%) MEA [ 2 (aq)] Absorbed (m) P2* (Pa)

16 Heat of Absorption Pa at 60 o 1.8 m PZ - H abs (kcal/mol 2 ) m K + /1.2 m PZ 5.0 m K + /2.5 m PZ 3.6 m K + Model Predictions 8 ther Model Predictions 3.6 m K + Experimental Points *[PZ] 2*[PZ] + [K + ]

17 ormalized Flux at 60 o 3.6 m K + /3.6 m PZ ormalized Flux (mol/pa-cm 2 -s) 1e M MEA 6.2 m K + /1.8 m PZ 3.6 m K + /0.6 m PZ 3.6 m K + /1.8 m PZ 5.0 m K + /2.5 m PZ 2.5 m K + /2.5 m PZ P 2 * (Pa)

18 Absorption Rate in 5.0 m K + /2.5 m PZ 1e-9 ormalized Flux (mol/cm 2 -Pa-s) 1e o 60 o 100 o 110 o 80 o P 2 * (Pa)

19 Research Activities at UT Bench-scale Wetted-wall olumn VLE, rates MR speciation Degradation ther solid solubility, transport properties Modeling Thermodynamics Rate Process Pilot Plant ontactor Testing Solvent Testing

20 xidative Degradation of MEA H 3 H H 2 H 2 H H ν 2? Formaldehyde Formate, Acetate Rate is measured by H 3 evolution from a sparged reactor vessel Gas analysis is quick/liquid analysis requires long experiments Uncertainty in the stoichiometry of 2 in the reaction

21 Degradation Results Study Sparge Gas Gas Flow/Liq. Vol (min -1 ) Max. Rate (mm/hr) Rooney et al. Air Blachly and Ravner Air Girdler 50% Hofmeyer et al. Pure hi and Rochelle Air Goff and Rochelle Air Air w/ Agitation onclusion: Mass Transfer Limited?

22 Process Modeling Explore ptimum perating onditions Heat requirement (kcal/gmol 2 ) ptimal MEA 40 Absorber 1.6 atm stripper optimum lean P* kpa lean loading (m) 5

23 Process onfiguration Explore unique flowsheets Multipressure Stripper Rich ldg= atm Lean ldg= atm 2.8 atm Multistage ompressor W=7.4 kc/mol 2 2 atm Q=20 kc/mol 2

24 Pilot Plant at UT-SRP 18 PV columns, 20 ft of packing Accommodates commercial, structured packing peration as absorber or absorber/stripper Vacuum stripping Air/ 2 Fed Wide Range of oncentrations Possible

25 Pilot Plant peration ah/air Screen packing areas Packing areas based on 0.75 H 2 /ft, 5 gpm/ft 2 Packing Wetted Area (ft 2 /ft 3 ) MR 2, plastic 27 IMTP #40 44 MR 2, metal 48 Montz B Montz B Solvent Simulation of absorber/stripper Quantify real solvent performance Includes impurities (Fe 2+, degradation, etc.)

26 onclusions E-RTL model describes speciation and VLE K + increases the amount of reactive species in solution 3 2- /H 3- is an effective buffer Apparent carbamate stability is increased w/ K + Solvent capacity increases with concentration and is comparable to MEA H abs can be lower than other amine-based systems and depends on the ratio of K + :PZ Absorption rate is 1.5 to 4 times faster than MEA or other amine-promoted K 2 3 solutions

27 Acknowledgements Texas Advanced Technology Program: contract George Goff Degradation Tunde yenekan Process Modeling Dr. Ben Shoulders The University of Texas at Austin, Department of hemistry

28 Questions?