CO2 Capture from Gasification Syngas

via Cyclic Carbonation / Calcination

Robert Symonds, University of Ottawa

SupervisorsDr. A. MacchiDr. E. J. Anthony

Robin HughesCANMETNRCan

Overview

Introduction• Hydrogen production in Canadian context

Objectives

Experimental Method

Results• Kinetic parameters

• Sorbent decay

• Morphology

• Observations

Operational CANMET pilot facilities for CO2 looping studies

Summer 2008 Testing

Introduction - Gasification

In Canada, very large quantities of H2 will be produced via gasification for heavy and ultra heavy oil upgrading, power production, and possibly transportation

• The production of syngas (mainly CO and H2) from a number of carbonaceous fuel sources including coal, petroleum coke, oil, asphaltenes, and biomass occurs via:

3C + O2 + H2O -> 3CO + H2

• The syngas can be shifted to hydrogen via the water-gas shift reaction in the presence of steam

CO + H2O -> CO2 + H2

• The production of hydrogen via gasification results in high CO2 emissions unless the CO2 can be sequestered

Oil Sands – Need low cost hydrogen Production and upgrading facilities are expected to grow by a factor of 5 over the next 25 years. Aggregate Production Forecast:2003 – 1.1 million b/d 2012 – 2.0 million b/d 2030 – 5.0 million b/d

• Natural gas price is volatile and supply will diminish;

• Will need alternative fuels (coal, petroleum coke and refinery residues) to meet the demand; however,

• Higher carbon fuels will increase CO2 emissions

H2 Production for Oil Sands using Gasification

H2 Production Comparison

• CO2 emissions are increased when producing H2 from asphaltenes and pet coke when compared to natural gas

• If 90% CO2 capture with gasification assumed then emissions are less than SMR with natural gas

• Gasification for hydrogen with CO2 capture and compression (ex. 150 bar) is less energy intensive and more cost effective

W/O CO2 Capture W/ 90% CO2 CaptureSource: White 2007, Air Products

CO2 emission, tonne/kNm3 H2

SMR, NG 0.9

Asphaltene gasification 1.3

Pet coke gasification 1.8

CO2 emission, tonne/kNm3 H2

SMR, NG 0.37

Asphaltene gasification 0.17

Pet coke gasification 0.19

Canadian Gasification with CCS

EPCOR - 90% CO2 capture• Genesee 4 – 500 MW coal IGCC for electrical

power production• Front end engineering design underway• FEED funding industrial/provincial/federal• 8000 TPD coal

Sherritt – ~4.5 Mt/yr CO2• Dodds-Roundhill – 270 MSCFD hydrogen

production via coal gasification• Hydrogen to be used for oil sands upgrading

Opti-Nexen – Long Lake project• Oil sands operator producing very high quality

synthetic crude oil• Gasifying asphaltenes for H2, steam, and

power• Phase I includes 4 Shell gasifiers

Introduction - CO2 Sorbents

Investigating methods for syngas CO2 separation that can be performed at high temperature and pressure• Metal oxides have high equilibrium capacities. • Can generate a nearly pure stream of CO2 (>85 %) needed for

sequestration

Objectives

• Determine the effect of ‘slagging gasifier’ syngas on carbonation reaction kinetics for naturally occurring calcium oxide based sorbents.

• Determine reaction kinetics for the development of a single phase, plug flow, moving bed carbonator reactor model.

• Perform sensitivity / parametric analysis of carbonator reactor model.

Experimental Equipment – TGA

Measurement Techniques – Limestone

)0()(

)0()(

3 CaOCaCO

CaOCaO

mmpurity

mtmX

−⋅−

=

13

15

17

19

21

23

25

0 1000 2000 3000 4000 5000

Time (s)

0

100

200

300

400

500

600

700

800

900

Experimental Conditions

Naturally occurring calcium oxide based sorbents• Havelock Limestone• Newfoundland Dolomite

Particle size range• 250 – 425 micron

0.20 0.06 42.99

0.17 1.30 21.25 30.51 0.15 0.04 44.40

0.34 0.30 0.29 54.10Havelock

Newfoundland Dolomite

1.90

2.12

Sorbent SiO 2 Al2O3 Fe 2O3 MgO CaO Na 2O K2O LOI

Experimental Conditions

Feed Gas – Carbonation• GE gasifier with Illinois bituminous coal as a feed (Simbeck et al., 1993)• CH4, H2S, NH3, and HCN have been omitted from the syngas feed stream

With CO and H2

Without CO and H2 0 0 0.17 0.75

H2O N2

0.08

0.08

0.42 0.21 0.17 0.12

CO2 CO H2Carbonation Feed Gas

Experimental Conditions

Temperature – Carbonation • 580, 620, 660, 700oC

Feed Gas – Calcination• N2

• CO2 and N2 (similar to Abanades et al., 2003)

Temperature - Calcination• 850 and 915oC

Atmospheric pressure, 10 cycles

Rate of Reaction

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 100 200 300 400 500 600

Time (s)

(1-(1-X)

1/3

)

With CO and H2

Without CO and H2

Reaction rate given bymaximum slope for grainmodel

Effect of Carbonation Feed Gas

• Presence of CO/H2 have increased the initial rate of carbonation by 70%

• Increased local CO2 concentration at CaO surface?

• Believe CaO or an impurity may be catalyzing the water-gas shift reaction• Calculated activation energies are 60.3 and 29.7 kJ/mol with and without the

presence of CO and H2 during carbonation

• Sun et al. (2008) determined activation energy was 29 ± 4 kJ/mol without CO/H2

ks (mol/m2.s.kPa)

620 0.0029 1.29E-06

Feed Gas Composition (vol%)

Total Pressure (atm) Temperature (oC) r0 (1/s)

8 CO 2, 21 H 2, 42 CO,

17 H2O, 12 N 2

8 CO 2, 17 H 2O, 75 N 2

1

1 620 0.0017 7.58E-07

Sorbent Decay

• Presence of CO and H2 during the carbonation of Havelock particles have little impact on the CaO conversion over 10 cycles

• Expected since particle sintering should be similar based on identical calcination conditions, but sorbent morphology indicates physical differences

fw

0.328

0.3248 CO 2, 17 H 2O, 75 N 2 1 620 0.74910

Temperature (oC) fm

8 CO 2, 21 H 2, 42 CO,

17 H2O, 12 N 21 620 0.749

N Cylces

10

Feed Gas Composition (vol%)

Total Pressure (atm)

Sorbent Decay - Gas Composition

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9 10

Cycle

Conversion

Without H2 and CO

With H2 and CO

TG850/0

Best Fit

Presence of Steam

• The presence of steam increases the carbonation conversion by approximately 30% at the end of the 10th cycle

• Several authors (Lin et al., 2005 and Gupta et al., 2002) observed a significant increase in CaO conversion via the intermediate formation of Ca(OH)2 but neither these processes lie within the carbonation conditions explored in this work

• In a recent study on sulphation under oxy-fired conditions evidence was advanced for the transient formation of Ca(OH)2, with an effect on carbonation (Wang et al., 2008)

• The addition of steam seems to result in the creation of larger pores

Sorbent Decay - Temperature

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9 10

Cycle

Conversion

580oC

620oC

660oC

700oC

250-425 micron Havelock calcined at 850 C with N2, carbonated with 8% CO2, 21% H2, 42% CO, 17% H2O, and 12% N2

Sorbent Morphology

Calcined at 850 C with N2 and carbonated at 580 C with 8% CO2, 17% H2O, and 75% N2

Calcined at 850 C with N2 and carbonated at 580 C with 8% CO2, 21% H2, 42% CO, 17% H2O, and 12% N2

After 10 cycles of calcination/carbonation

Sorbent Morphology

Calcined at 850 C with N2 and carbonated at 580 C with 8% CO2, 17% H2O, and 75% N2

Calcined at 850 C with N2 and carbonated at 580 C with 8% CO2, 21% H2, 42% CO, 17% H2O, and 12% N2

After 10 cycles of calcination/carbonation

Calcination

• Under a 90% percent atmosphere of CO2, the initial rate of carbonation is 1/5 that of calcination with pure N2.

• It is known that during sintering, necks develop between adjacent micrograins and continue to grow. The material for this is supplied from the rest of the micrograin, so that the distance between grain centers is diminished. This causes both the voidage and the surface area to decrease (Stanmore and Gilot, 2005).

2.23E-06

ks (mol/m2.s.kPa)

4.91E-07

100 N2 1 915 0.0050

90 CO 2, 10 N 2 1 915 0.0011

Feed Gas Composition (vol%)

Total Pressure (atm) Temperature (oC) r0 (1/s)

Sorbent Morphology

• Images after first calcination/carbonation cycle• Calcined at 915 C and carbonated at 620 C with 8% CO2, 21%

H2, 42% CO, 17% H2O, and 12% N2

Calcined under N2; kept under CO2 until temperature ready for calcine

Calcined under 90% CO2; balance N2

CO2 Looping Cycle Pilot Plant

Sorbent

Flue Gas

Fuel

FreshLoadedRegenerated

CoalCoke

AirOxygen

Low CO2 (< 5%)High CO2 (~92%)

Oxidant Oxy-Fuel CFB

Calciner

Air Blown Combustor

Carbonator

Our small oxy-fuel CFBC

Current Configuration• 5 m in height, 0.1 m ID

• 18 kW of electric heaters surrounding dense bed region

• Primary and secondary oxidant ports with flue gas dilution

• Independent fuel and sorbent injection

• Recycle system includes condenser, condensate KO, and blower

• Utilities include steam, water & air

• Fluidizing gas 65+ mol% O2

• BFB or CFB

Oxy-Fired Circulating Fluidized Bed (CFB)

• 10 m; 0.6 m ID• Maximum oxygen flow

250 kg/hr• Currently set up for a

maximum oxygen concentration of 27 mol%

• 1 m BFB adjacent with solids transport lines

• BFB opeated as a gasifier or combustor

• Previously operated as an Exxon style fluid bed coker (5 years)

• Proposal submitted for CO2 looping in this facility

Effect of Hydration

0 10 20

Cycle Number

0.0

0.2

0.4

0.6

0.8

1.0

Conversion, X

N

• Hydrated Cadomin limestone derived sorbent conversion to CaCO3 at various conditions

• Conversion as high as 0.57 after 20 cycles

• Sorbent was likely too friable for commercialization

• No SO2 in sample gases

• Calcined in N2

Sorbent Pelletization

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3

Crushed, 600-1400 micronPowder, 25-100 micronPellet, Binder: WaterPellet, Binder: Water & 5% Na2CO3Pellet, Binder: Water & Na BentonitePellet, Binder: Water & Ca Bentonite

Conversion

Cycle Number

Pilot Scale Work Summer 2008

Objective• Investigate CO2 capture processes at pilot scale under

atmospheric pressure; flue gas & syngas

Experimental equipment• Batch or continuous operations in 0.1 m ID fluidized

beds• Calcine with oxy-fired wood pellets with recycled flue

gas (dry recycle, O2 up to 65 mol%)• Carbonate with mildly fluidized or moving bed gas

velocities• Rotary tube furnace

• Pretreatment or periodic treatment• Max 1400 C; 21 kW• 1 m heated length; 1 - 5 rpm• Can add steam etc. to heated zone

Early results• Tests to date with air/CO2/H2O• Steam allowing CO2 capture at equilibrium levels even

below 580 C

Contact

Robin Hughes, CANMETrhughes@nrcan.gc.ca

Dr. E. J. Anthony, CANMETbanthony@nrcan.gc.ca

Results and Discussion – Comparison of Calcium Oxide based Sorbents

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1 2 3 4 5 6 7 8 9 10

Cycle

Conversion

Limestone

Dolomite

Results and Discussion – Naturally Occurring Dolomite

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9 10

Cycle

Conversion

Without CO and H2

With CO and H2

Results and Discussion – Comparison of Calcium Oxide based Sorbents

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

1 10 100 1000

Pore Diameter (nm)

Pore Volume (cm

3/g.nm) Havelock

N. Dolomite

Carbonation Temp Havelock Limestone

y = -7254.5x - 5.54

R2 = 0.9688

-14.2

-14.0

-13.8

-13.6

-13.4

-13.2

-13.0

-12.8

0.001 0.00104 0.00108 0.00112 0.00116 0.0012

1/T (1/K)

ln(k

s)