“CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO" B. Arias, J.M. Cordero, M. Alonso, J.C. Abanades CO 2 Capture Group National Institute of Coal (INCAR-CSIC) Trondheim CO 2 Capture, Transport and Storage Conference 14-16 June, Trondheim, Norway
OUTLINE • Introduction • Objectives • Experimental Thermogravimetric analysis • Small pilot plant of 30 kWt • • Results and discussion Sulfation rates • SO 2 retention under carbonation conditions • • Conclusions Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
SO 2 on Ca-looping post-combustion systems Flue gas Concentrated CO 2 “without” CO 2 CaCO 3 Flue Gas POWER PLANT CARBONATOR CALCINER O 2 CO 2 CaO SO 2 Air ASU Coal Coal Air CaCO 3 CaO N 2 ( Sulfur ) ( Sulfur ) (F 0 ) Purge Reaction of CaO with SO 2 : SO 2 reduces maximum CO 2 carrying capacity • CaO is being used routinely as desulfurization Previous agent in CFB combustors findings • Main differences between SO 2 capture in CFBC and carbonator: Sulfation behavior of CaO is • Range of temperatures enhanced during cycling • Range of conversion ¿Sulfation rates of cycled CaO at carbonation • Texture of CaO conditions and SO 2 capture efficiency? Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Outline • Introduction • Objectives • Determination of sulfation rates of cycled CaO particles under carbonation conditions • Study the SO 2 capture efficiency in a CFB carbonator • Experimental • Results and discussion • Conclusions Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Experimental facilities Thermo-gravimetric analyzer 30 kWt Pilot Plant at INCAR-CSIC Experimental conditions during TGA tests • Mixtures of air/CO 2 /SO 2 • Calcination: T=950 ºC, Air • Carbonation: T=650 ºC, 10% CO 2 in air Main characteristics: • Sulfation: T=650 ºC, SO 2 =500-3000 ppm • Two CFB reactors (Height~6.5 m, diameter=100 mm) • Number of cycles up to 50 • Electrically heated • Three different limestones • Measurement port (temperature, pressure, gas composition) • Solid circulation measurements Al 2 O 3 CaO Fe 2 O 3 K 2 O MgO Na 2 O SiO 2 TiO 2 • Solid samples characterization (TG analysis, C/S analyzer) Compostilla 0.16 89.7 2.5 0.46 0.76 <0.01 0.07 0.37 Imeco 0.10 96.1 0.21 0.05 1.19 0.01 1.11 <0.05 Trondheim CCS Conference Enguera 0.18 98.9 <0.01 0.03 0.62 0.00 0.43 0.02 CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Experimental results: Sulfation rates Effect of number of cycles on sulfation behavior Effect of SO 2 concentration on CaO sulfation 0.4 Sulfation conditions: T=650 ºC, SO 2 =500 ppm v 0.3 0.35 Compostilla Imeco 0.30 XCaSO4 Enguera Compostilla 0.2 0.25 limestone (N=1) Fresh calcined X CaSO4 0.20 500 ppm 0.1 limestone 1000 ppm 0.15 2000 ppm 3000 ppm 0.10 0.0 0.05 N=1 0 500 1000 1500 2000 Time (s) 0.00 0 300 600 900 1200 Time (s) Determination of reaction order respect to SO 2 0.25 Compostilla 3.0E-03 Imeco Enguera 0.20 2.5E-03 0.15 X CaSO4 ∆ X CaSO4 / ∆ t (s -1 ) 2.0E-03 After 20 cycles 0.10 1.5E-03 0.05 1.0E-03 N=20 Compostilla N=1 Imeco N=1 5.0E-04 0.00 Enguera N=1 0 300 600 900 1200 Compostilla N=20 Time (s) 0.0E+00 0 0.01 0.02 0.03 0.04 • No pore plugging is present during sulfation of cycled C SO2 (mol/m3) particles up to reaction times of 20 min. • Results show that sulfation of CaO is a first reaction order Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Experimental results: Sulfation rates Interpretation of experimental data: Application of the Random Pore Model General expression of RPM Chemically controlled Chemically/Diffusion ( ) reaction (k s ) controlled reaction (k s , D) − ψ − k S C 1 ln 1 X dX s = ( ) β dt Z ( ) ( ) 2 − β Z 2 τ − ε + − ψ − − 1 1 1 ln 1 X 1 + β τ − ψ 1 Z 1 − ψ + 1 1 ψ N ψ 1 N 2 = − − N X 1 exp = − X 1 exp ( ) ψ 2 β Z ψ N N 1 2 [ ] 1 k S C t ( ) [ ] − ψ − − = s 1 ln 1 X 1 1 S D M C t ( ) ( ) ψ − ε − ψ − − = CaO 2 1 1 ln 1 X 1 ( ) ψ − ε ρ 1 2 Z CaO Derivation of reaction rate parameters k s Main model parameters: 0.3 1 • k s : reaction rate of surface reaction CaO conversion 0.2 • D: effective product layer diffusion • ψ : structural parameter 0.1 2 D 0 0 300 600 900 1200 Time (s) Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Experimental results: Sulfation rates RPM model results Comparison of experimental and calculated values using the RPM model Reaction rate parameters for studied limestones 0.4 N=50 Compostilla Compostilla Imeco Enguera N=20 0.3 k s0 (m 4 /mols) 6.38E-06 7.31E-06 8.31E-06 E ak (kJ/mol) 56 56 56 X CaSO4 0.2 D 0 (m 2 /s) 1.71E-05 1.49E-05 3.02E-05 E aD (kJ/mol) 120 120 120 0.1 h (nm) 8.6 7.0 9.9 0 0 300 600 900 1200 Time (s) 0.4 N=50 Enguera N=20 For practical application purposes in a 0.3 Ca-looping, only the chemically X CaSO4 controlled stage can be considered 0.2 ( ) − − ψ − k S C ( 1 X ) 1 ln 1 X dX 0.1 = s ( ) − ε dt 1 0 0 300 600 900 1200 Trondheim CCS Conference Time (s) CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO • Introduction • Objectives • Experimental Thermogravimetric analysis • Experiments in small pilot plant • • Results and discussion Determination of sulfation rates • SO 2 retention in a CFB carbonator in presence of CO 2 • • Conclusions Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Experimental results: SO 2 retention in a circulating fluidized bed carbonator bed 30 kWt Pilot Plant at INCAR-CSIC Gas from Gas from calciner carbonator CARBONATOR CALCINER -CARBONATADOR CALCINADOR CALCINER – CALCINER COMBUSTOR CARBONATOR CARBONATOR COMBUSTOR Air Air inlet inlet Coal Air Air CO 2 SO 2 Trondheim CCS Conference CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
Experimental results: SO 2 retention in a circulating fluidized bed carbonator bed EXAMPLE OF SO 2 CAPTURE EFFICIENCY SO 2 mass balance during the experimental Experimental conditions* testing period 14 - Flow to carbonator: 19 m 3 N/h - Solid circulation = 1.9 kg/m 2 s 12 - u gas =2.5 m/s - X sulf = 0.08 Carbonator Calciner 10 - CO 2 inlet concentration = 12% - X max -X carb = 0.03 %CaSO 4 calculated - SO 2 inlet concentration : - T carbonator = 668 ºC 8 1900 ppm (1) *Average values during experimental period shown 6 3800 ppm (2) 4 CO2 O2 SO2 25 1500 2 1 2 1 2 1 SO 2 concentration (ppm) 20 Volume fraction (%) 0 1000 0 2 4 6 8 10 12 14 15 % CaSO 4 experimental 10 500 5 0 0 1.0 16:40 16:55 17:09 17:24 17:38 17:52 18:07 SO 2 capture efficiency CO2 SO2 1 1.00 SO 2 capture efficiency CO 2 capture efficiency 0.9 0.8 0.98 SO2 capture efficiency 0.6 0.96 0.8 0.4 0.94 0.2 0.92 0.7 0 0.90 16:40 16:55 17:09 17:24 17:38 17:52 18:07 Inventory of solids (kg/m 2 ) 500 0.6 0 0.25 0.5 0.75 1 1.25 1.5 400 WCaO*Xave/FSO2 W CaO X ave /F SO2 (h) 300 200 100 Trondheim CCS Conference 0 16:40 16:55 17:09 17:24 17:38 17:52 18:07 CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO
CONCLUSIONS Sulfation of CaO cycled particles proceeds through an initial chemically controlled step followed by a second period where chemical reaction and diffusion through the product layer are the controlling resistances. Sulfation of CaO has been found to be a first reaction order with respect to SO 2 under carbonation conditions. Cycled particles do not undergo pore plugging due to the growth of the CaSO 4 layer during sulfation (for reaction times up to 20 min). The random pore model has been used to study the sulfation behavior of three limestones. Good agreement between experimental and calculated values has been found confirming the suitability of this model to describe the sulfation reaction under both reaction regimes. Post-combustion Ca-looping carbonators can be effective reactors for capturing SO 2 from flue gases even for low inventories of solids.
“CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator reactor of CaO" Thank you for your attention borja@incar.csic.es • This work has been carried out as part of the FP7 “CaOling“ Project. Trondheim CO2 Capture, Transport and Storage Conference 14-16 June, Trondheim, Norway
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