CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator - - PowerPoint PPT Presentation

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CO 2 and SO 2 co-capture in a circulating fluidized bed carbonator - - PowerPoint PPT Presentation

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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

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SLIDE 1

“CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO"

  • B. Arias, J.M. Cordero, M. Alonso, J.C. Abanades

CO2 Capture Group National Institute of Coal (INCAR-CSIC)

Trondheim CO2 Capture, Transport and Storage Conference

14-16 June, Trondheim, Norway

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SLIDE 2

OUTLINE

  • Introduction
  • Objectives
  • Experimental
  • Thermogravimetric analysis
  • Small pilot plant of 30 kWt
  • Results and discussion
  • Sulfation rates
  • SO2 retention under carbonation conditions
  • Conclusions

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

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SLIDE 3

SO2 on Ca-looping post-combustion systems

CARBONATOR POWER PLANT Concentrated CO2 CaCO3 (F0) CaO Purge CaCO3 CaO Flue Gas Flue gas “without” CO2 Coal (Sulfur) Air O2 Air N2 ASU CALCINER CO2 SO2 Coal (Sulfur) SO2 reduces maximum CO2 carrying capacity Sulfation behavior of CaO is enhanced during cycling

¿Sulfation rates of cycled CaO at carbonation conditions and SO2 capture efficiency?

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

Reaction of CaO with SO2:

  • CaO is being used routinely as desulfurization

agent in CFB combustors

  • Main differences between SO2 capture in CFBC

and carbonator:

  • Range of temperatures
  • Range of conversion
  • Texture of CaO

Previous findings

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SLIDE 4

Outline

  • Introduction
  • Objectives
  • Determination of sulfation rates of cycled CaO particles under

carbonation conditions

  • Study the SO2 capture efficiency in a CFB carbonator
  • Experimental
  • Results and discussion
  • Conclusions

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

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SLIDE 5

Experimental facilities Thermo-gravimetric analyzer 30 kWt Pilot Plant at INCAR-CSIC

Main characteristics:

  • Two CFB reactors (Height~6.5 m, diameter=100 mm)
  • Electrically heated
  • Measurement port (temperature, pressure, gas composition)
  • Solid circulation measurements
  • Solid samples characterization (TG analysis, C/S analyzer)

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

Experimental conditions during TGA tests

  • Mixtures of air/CO2/SO2
  • Calcination: T=950 ºC, Air
  • Carbonation: T=650 ºC, 10% CO2 in air
  • Sulfation: T=650 ºC, SO2=500-3000 ppm
  • Number of cycles up to 50
  • Three different limestones

Al2O3 CaO Fe2O3 K2O MgO Na2O SiO2 TiO2 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 Enguera 0.18 98.9 <0.01 0.03 0.62 0.00 0.43 0.02

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SLIDE 6

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

0.0E+00 5.0E-04 1.0E-03 1.5E-03 2.0E-03 2.5E-03 3.0E-03 0.01 0.02 0.03 0.04 CSO2 (mol/m3) ∆XCaSO4/∆t (s-1)

Compostilla N=1 Imeco N=1 Enguera N=1 Compostilla N=20

Experimental results: Sulfation rates

0.0 0.1 0.2 0.3 0.4 500 1000 1500 2000 Time (s) XCaSO4 500 ppm 1000 ppm 2000 ppm 3000 ppm

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 300 600 900 1200 Time (s) XCaSO4 Compostilla Imeco Enguera

N=1

Effect of number of cycles on sulfation behavior

0.00 0.05 0.10 0.15 0.20 0.25 300 600 900 1200 Time (s) XCaSO4 Compostilla Imeco Enguera

N=20

Sulfation conditions: T=650 ºC, SO2=500 ppmv Fresh calcined limestone After 20 cycles Effect of SO2 concentration on CaO sulfation Compostilla limestone (N=1) Determination of reaction order respect to SO2

  • No pore plugging is present during sulfation of cycled

particles up to reaction times of 20 min.

  • Results show that sulfation of CaO is a first reaction order
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SLIDE 7

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

Experimental results: Sulfation rates

( ) ( ) ( )

( )

     − − ψ − ψ β + ε − − ψ − = 1 X 1 ln 1 Z 1 1 X 1 ln 1 C S k dt dX

s

Interpretation of experimental data: Application of the Random Pore Model

                    + − − =

N N

X ψ ψ τ

2

1 2 1 exp 1

( )

                              − − + − − =

2 2

1 1 1 exp 1 Z Z Z X

N N N

β ψ ψ β τ β ψ

Chemically controlled reaction (ks) Chemically/Diffusion controlled reaction (ks, D)

0.1 0.2 0.3 300 600 900 1200 Time (s) CaO conversion

Derivation of reaction rate parameters

General expression of RPM

1 2 1

ks

2

D

( )

[ ]

( )

ε − = − − ψ − ψ 1 2 t C S k 1 X 1 ln 1 1

s

( )

[ ]

( )

Z 2 t C M D 1 S 1 X 1 ln 1 1

CaO CaO

ρ ε − = − − ψ − ψ

Main model parameters:

  • ks: reaction rate of surface reaction
  • D: effective product layer diffusion
  • ψ: structural parameter
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SLIDE 8

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

Experimental results: Sulfation rates

Compostilla Imeco Enguera ks0 (m4/mols) 6.38E-06 7.31E-06 8.31E-06 Eak (kJ/mol) 56 56 56 D0 (m2/s) 1.71E-05 1.49E-05 3.02E-05 EaD(kJ/mol) 120 120 120 h (nm) 8.6 7.0 9.9

RPM model results Reaction rate parameters for studied limestones

0.1 0.2 0.3 0.4 300 600 900 1200 Time (s) XCaSO4 N=50 N=20 0.1 0.2 0.3 0.4 300 600 900 1200 Time (s) XCaSO4 N=50 N=20

Enguera Compostilla For practical application purposes in a Ca-looping, only the chemically controlled stage can be considered

( ) ( )

ε ψ − − − − = 1 1 ln 1 ) 1 ( X X C S k dt dX

s

Comparison of experimental and calculated values using the RPM model

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SLIDE 9

CO2 and SO2 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
  • SO2 retention in a CFB carbonator in presence of CO2
  • Conclusions

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

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SLIDE 10

Experimental results: SO2 retention in a circulating fluidized bed carbonator bed

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

COMBUSTOR – CALCINER Air inlet CARBONATOR CALCINADOR COMBUSTOR

  • CARBONATADOR

CALCINER Air inlet CARBONATOR

CARBONATOR CALCINER

Air Coal Air CO2 SO2

30 kWt Pilot Plant at INCAR-CSIC

Gas from calciner Gas from carbonator

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SLIDE 11

Experimental results: SO2 retention in a circulating fluidized bed carbonator bed

Trondheim CCS Conference

CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO

0.2 0.4 0.6 0.8 1 16:40 16:55 17:09 17:24 17:38 17:52 18:07 CO2 capture efficiency 0.90 0.92 0.94 0.96 0.98 1.00 SO2 capture efficiency CO2 SO2 5 10 15 20 25 16:40 16:55 17:09 17:24 17:38 17:52 18:07 Volume fraction (%) 500 1000 1500 SO2 concentration (ppm)

CO2 O2 SO2 1 2 1 2 1 100 200 300 400 500 16:40 16:55 17:09 17:24 17:38 17:52 18:07

Inventory of solids (kg/m2)

  • Solid circulation = 1.9 kg/m2s
  • Xsulf = 0.08
  • Xmax-Xcarb = 0.03
  • Tcarbonator = 668 ºC

*Average values during experimental period shown

Experimental conditions*

  • Flow to carbonator: 19 m3N/h
  • ugas=2.5 m/s
  • CO2 inlet concentration = 12%
  • SO2 inlet concentration:

1900 ppm (1) 3800 ppm (2)

EXAMPLE OF SO2 CAPTURE EFFICIENCY

2 4 6 8 10 12 14 2 4 6 8 10 12 14 % CaSO4 experimental %CaSO4 calculated Carbonator Calciner

SO2 mass balance during the experimental testing period

0.6 0.7 0.8 0.9 1.0 0.25 0.5 0.75 1 1.25 1.5

WCaO*Xave/FSO2 SO2 capture efficiency

WCaO Xave/FSO2 (h) SO2 capture efficiency

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SLIDE 12

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 SO2 under carbonation conditions.

Cycled particles do not undergo pore plugging due to the growth of the CaSO4 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 SO2 from flue gases even for low inventories of solids.

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SLIDE 13

Thank you for your attention

borja@incar.csic.es

  • This work has been carried out as part of the FP7 “CaOling“ Project.

“CO2 and SO2 co-capture in a circulating fluidized bed carbonator reactor of CaO"

Trondheim CO2 Capture, Transport and Storage Conference

14-16 June, Trondheim, Norway