2nd Workshop

International Oxy-Combustion Research Network Hilton Garden Inn Windsor, CT, USA

25th and 26th January 2007

Hosted by:

Alstom Power Inc.

PRESENTATION - 17

Chemical-Looping Combustion Using Gaseous and Solid Fuels

by: Tobias Mattisson Chalmers University, Sweden

2nd Int'l Oxy-Combustion Workshop Page 1

CHEMICAL-LOOPING COMBUSTION USING GASEOUS AND SOLID FUELS

Tobias Mattisson, Chalmers University of Technology

Göteborg, Sweden

Chemical-looping combustion

● A process for oxidizing fuels using metal oxides as oxygen carriers, transferring oxygen from combustion air to fuel.

● No mixing of combustion air and fuel => CO2 can be obtained pure, without (!) separation of gases

2nd Int'l Oxy-Combustion Workshop Page 2

CH4

CO2 H2O

O2N2

N2

MexOy

MexOy-1

Fuel-reactor

Air-reactor

air

flue gas

fuel

1

3

2

CO2, H2O

4

4

1

1 air reactor, riser2 cyclone3 fuel reactor4 particle locks

2nd Int'l Oxy-Combustion Workshop Page 3

Chemical-looping combustion, status 2002: • ”paper concept”, • process never tested • a limited number of particles tested in a

limited number of cycles What has happened since then ?

>300 particles have been tested: • active oxides primarily NiO, CuO, Mn3O4, Fe2O3 • support materials, e.g. Al2O3, TiO2, SiO2, ZrO, sepiolite,

MgAl2O4 ... • various mixing ratios active oxide/support • production methods: extrusion, freeze-granulation, wet

methods, impregnation ... • heat treatment: typically 900-1300 C • tests performed in batch fluidized bed reactors, TGA,

continuous CLC reactors

2nd Int'l Oxy-Combustion Workshop Page 4

Pros and cons for the active oxides Fe Mn Cu Ni Reactivity -- - + ++ Cost ++ + - -- Health - Thermodynamics -1 Reaction with CH4 +2 Melting point -3 1maximum conversion 99-99.5% 2exothermic reaction in fuel reactor 3melting point Cu: 1085 C

Iron ore

BET=3,7 m2/g

Pore volume=0,012 cm3/g

Impregnated

BET=80,8 m2/g

Pore volume=0,35 cm3/g

Three different types of oxygen carriers based on Fe2O3

Freeze granulated

BET=8,3 m2/g (high)

Pore volume=0,33 cm3/g

2nd Int'l Oxy-Combustion Workshop Page 5

0 20 40 60 80 100Time (s)

0

0.2

0.4

0.6

0.8

1

Con

vers

ion

Effect of temperature on the reduction reaction using CH4 (10%) at 800°C (▲), 850°C (∆), 900°C (+), 950°C (●) and 1000°C (○).Continuous line: results predicted by shrinking-core model for spherical grains.

Results from reactivity investigation (TGA) of an oxygen carrier of NiO/MgAl2O4 produced by freeze granulation

Solid inventory as a function of solid conversion at the inlet of fuel reactor (Xo,inFR) and air reactor (Xo,inAR) mFR (∆),mAR (▲) and mtotal (●).

How much material of this carrier is needed in the fuel and air reactor?

0 0.2 0.4 0.6 0.8 1Xo,in FR

0

20

40

60

80

100

Solid

inv

ento

ry (k

g/M

WFu

el)

0.02 0.22 0.42 0.62 0.82Xo,in AR

2nd Int'l Oxy-Combustion Workshop Page 6

a) the lower part, frontview b) entire reactor, frontview c) entire reactor, sideview Figure 2. The principal sketch of the reactor. 1) air reactor, 2) downcomer, 3) fuel reactor, 4) slot, 5) gas distributor plate, 6) wind box, 7) reactor part, 8) particle separator, 9) leaning wall. Fluidization in the downcomer (x) and slot (o) is also indicated. The dashed lines indicates the bed heights during combustion.

88

7

8

7 7

9 91

2

3

4

56 6

x

Small 300 W chemical-looping combustor

Chalmers’ 300 W chemical-loopingcombustor 2004

2nd Int'l Oxy-Combustion Workshop Page 7

0.001

0.01

0.1

1

10

100

750 800 850 900 950

Temperature ( C)

frac

tion

(%)

750 800 850 900 950

Temperature ( C)750 800 850 900 950 1000

Temperature ( C)

Ni Mn Fe

Results from tests in 300 W continuous reactor with three types of particles using natural gas

Chalmers’ 10 kW chemical-looping combustor 2003

convectivecooling of flue gases

reactorsystem

filters

2nd Int'l Oxy-Combustion Workshop Page 8

Conclusions (Ni-based particles): No CO2 from air reactor: • No leakage between reactors • No significant carbon formation • 100% CO2 capture

Sand tests show no leakage from air to fuel reactor: • Almost pure CO2 possible

1.2% H2, 0.6% CO with NiO Conversion of fuel: • 99.5% at 800

Operation • Stable and easy to control • 105 h operation CLC (13 days) without change of particles • ~300 h circulation Investigation of particles after 105 h • No loss in reactivity • No loss in particle strength Loss of fines very low: • Particle lifetime >40,000 h (?) Low particle cost: • <1 €/ton CO2 (lifetime 4,000 h)

2nd Int'l Oxy-Combustion Workshop Page 9

Chemical looping reforming by

partial oxidation

Hydrogen production by steam reformingwith chemical-looping as heat source and

separation off-gas as fuel.

Hydrogen production using chemical-looping technology

air

flue gas

fuel

1

3

2

CO2, H2O

4

4

1

1 air reactor, riser2 cyclone3 fuel reactor4 particle locks

Solid fuels application • Solid fuels reacts indirectly with

ox.carrier, via gasification step • Char may follow particles to air

reactor => incomplete capture • Gasification slow => large residence

time => large solids inventory in fuel reactor

• Less effective contact between fuel gas and oxygen carrier

• Ash may reduce oxygen carrier life-time

2nd Int'l Oxy-Combustion Workshop Page 10

Fundamental principles

Gasification

Chemical-looping combustion

Char is gasified in environment of highly reducing gas, in order to achieve gas with high heating value. => low concentration of reacting gas (H2O, CO2), high concentration of inhibitor (H2, CO)

Char is gasified in environment of oxidizing gas (H2O + CO2), with rapid removal of gasification products (CO, H2) already inside the particle phase => high concentration of reacting gas (H2O, CO2), low concentration of inhibitor (H2, CO) => much higher rate of conversion => may avoid negative effects of reducing conditions on ash

0 5 10 15 20Time [ minutes ]

0

0.02

0.04

0.06

0.08

Con

cent

ratio

n [ -

]

CO2

CO

CH4/SO2

Concentration profile during the reduction of Fe2O3/MgAl2O4 with petroleum coke. The inlet H2O content is 50% and SO2 0%. The temperature is 950˚C.

• Laboratory tests of solid fuel (pet. coke) and metal oxide particles verify concept. Air / solid fuel were added in cycles. • Same metal oxide particles were used in 100 h of testing with varying temperature, steam conc., SO2 conc., defluidization.

2nd Int'l Oxy-Combustion Workshop Page 11

Effect of steam concentration on rate of reaction between petroleum coke and an oxygen carrier of Fe2O3/MgAl2O4

Taken from Leion et al., 2006 (in press)

Chalmers’ 10 kW chemical-looping combustor for solid fuels, 2005

2nd Int'l Oxy-Combustion Workshop Page 12

Testing in chemical-looping combustors: unit particle operation h

(hot timed) fuelf

1 aChalmers 10 kW NiO/NiAl2O4 105 (300) n.gas 2a aChalmers 10 kW Fe2O3-based 17 n.gas 2b Chalmers 10 kW Fe2O3-based 16 n.gas. 3 aS Korea 50 kW Co3O4/CoAl2O4 25 n.gas 4 aS Korea 50 kW NiO/bentonite 3i n.gas. 5 bChalmers 300 W NiO/NiAl2O4 8 (18)g n.gas 6 bChalmers 300 W NiO/MgAl2O4 30 (150) n.gas/syngas 7 bChalmers 300 W Mn3O4/ ZrO2, Mg-st. 70 (130) n.gas/syngas 8 cChalmers 300 W Fe2O3/Al2O3 40 (60) n.gas/syngas 9 bCSIC, 10 kW CuOimpregnated 2x100 n.gas 10 bChalmers 300 W NiO/MgAl2O4 41 (CLR g) n.gas(CLR g) 11 Chalmers SFj confidential 18 bit. coal apublished 2004, bpublished/accepted 2005-2006, csubmitted d total time fluidized at high temperature, esame particle as used 100 h in 10 kW unit, fn.g. = natural gas, s.g. = syntesgas, gchemical-looping reforming, iparticles fragmentated, j10 kW solid fuel CLC,

Chemical-Looping Combustion

Reactor system (fluidized beds): - well established - commercially available - simple - moderate costs

Oxygen-carrier particles: - very encouraging results - scale-up of particle manufacture - raw materials

- long-term testing needed

2nd Int'l Oxy-Combustion Workshop Page 13

Applications of chemical-looping combustion for CO2 capture:

Combustion of gaseous fuel, natural gas, refinery gas, syngas Chemical-looping reforming, i.e. hydrogen production Combustion of solid fuels