chemical looping combustion and reforming at a 120 kw ... septiembre/c32.pdf · →thermodynamic...

Chemical looping combustion and reforming at a 120 kW pilot plant – results

using a nickel-based oxygen carrier

Tobias Pröll, Philipp Kolbitsch, Johannes Bolhàr-N., Hermann Hofbauer

Vienna University of Technology

1st IEA GHG High Temperature Solid Looping Cycles MeetingOviedo, Spain

Sept. 15-17, 2009

Tobias Pröll, Vienna University of Technology www.chemical-looping.at 2

Outline

Short introduction to chemical looping combustion

The pilot unit at Vienna Univ. Technol.

Results from the pilot unit:

→ Chemical Looping Combustion

→ Chemical Looping Reforming

Conclusions and outlook


Chemical looping combustion (CLC)

A new process for oxidizing fuels using metal oxides as oxygen carrierstransporting oxygen from combustion air to fuelNo mixing of combustion air and fuel, combustion products (CO2 and H2O) not diluted by N2

Highly exothermal reactions in air reactor

Global heat release equal to that of direct combustion

Air reactor(AR)

Fuel reactor(FR)

MeOx

MeOx-1

Air

N2, (O2)CO2, (H2O)

Fuel

Cooling/ condensation

CO2

H2O

CLC shows unique potential for carbon capture because gas-gas separation is inherently avoided.

Global air/fuel

ratio

> 1


Overall reactions in CLC

Fuel reactor reactions:

→ Chemical looping

reforming

dominated

by: •

partial oxidation

•

steam

reforming•

dry

reforming

Air reactor reaction:Air reactor

(AR)Fuel reactor

(FR)

MeOx

MeOx-1

Air

N2, (O2)CO2, (H2O)

Fuel

Cooling/ condensation

CO2

H2O


Critical issues in CLC

Oxygen carrier particles→ thermodynamic suitability→ high reactivity→ sufficient transport capacity→ high mechanical stability→ cyclic stability of reactivity and transport capacity

Reactor system→ excellent gas-solids contact in both reactors→ sufficient solids circulation rate


Outline








Dual circulation fluidized bed (DCFB) reactor system

→Global solids circulation is controlled by primary reactor fluidization only (eg. air staging)

→Secondary reactor can be optimized towards fuel conversion

→ Inherent stabilization of global solids hold up due to the direct hydraulic link between the reactors

→Low reactor volume compared to bubbling fluidized beds (i.e. low specific solids inventory)

→High potential for scale-up


120 kW plant design

bottom end = loop sealsupport fluidization in legs to lower loop seal (steam)air reactor net height: 4 mfuel reactor net height: 3 mdesign fuel: natural gasalternative fuels: CO+H2, C3H8

design particle size: 120 µm

Cooling system: water/steam and air

Exhaust gas cleanup: post combustion boiler, bag filter

air

steam

steam

steamfuel

gas

FR exhaustAR exhaust

steamsteam


Laboratory Arrangement

AR FR

bag filter

fire tube boiler

feed water

steam

steam, air fuel, steam, Ar

AR exhaustFR exhaust

solids loop


120 kW unit


Outline








Pressure profile in the DCFB systemCH4

fuel power: 140 kW; global air ratio: 1.1

0

1

2

3

4

5

0 5 10 15 20System pressure relative to atmosphere [kPa]

Rea

ctor

hei

ght [

m] air reactor

fuel reactorloop seals

AR cyclone exit

AR top

AR bottomFR bottom

FR top

FR cycl. exit downcomer AR

downcomer FR

upper loop seal

lower loop seal

FR int. loop seal


Fuel conversion performance

NiO-based oxygen carrierPth = 145 kW for natural gasPth = 127 kW for propaneglobal air ratio = 1.1

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

750 800 850 900 950 1000

Temperature [°C]

CH

4 con

vers

ion

and

CO

2 yie

ld [m

ol/m

ol]

X_CH4_65kg

Y_CO2_propane

Y_CO2_65kg

XCH4

γCO2 (C3H8)

γCO2 (CH4)

λ = 1.1

24

4

41

COCOCH

CHCH yyy

yX

++−=

24

2

2

COCOCH

COCO yyy

y++

=γ

Methane

conversion:

CO2

-yield:

Pröll, T., Kolbitsch, P., Bolhàr-Nordenkampf

J., Hofbauer, H., 2008, "A dual circulating

fluidized

bed

(DCFB) system

for

chemical

looping

combustion", AIChE

2008 Annual

Meeting, Philadelphia.


Fuel power variation at 900°C

0.70

0.75

0.80

0.85

0.90

0.95

1.00

50 75 100 125 150Fuel power [kW]

XC

H4 [

-], γ

CO

2 [-]

CH4 conv.

CO2 yield

global air ratio = 1.08 ± 0.04TFR = 1174 K ± 6 K

Pröll, T., Kolbitsch, P., Bolhàr-Nordenkampf

J., Hofbauer, H., "A dual circulating

fluidized

bed

(DCFB) system

for

chemical

looping

combustion", AIChE

Journal, in press, 2009.


Conclusions CLCDCFB reactor system:→scale-up ready candidate for large scale chemical looping

application

120 kW test unit / NiO-based oxygen carrier:→no detectable carbon leakage to the air reactor: 100% capture→CH4

conversion up to 99% →CO2

yield up to 96% based on total carbon in fuel→high fuel conversion in spite of the limited riser heights

Further work:→oxygen

carrier

materials

performance/cost

ratio→detailed

reactor

design

issues→scale

up to pilot/demonstration

size

(next

step: 10 MW)


Chemical looping reforming (CLR)

Less oxygen supplied than needed for complete oxidation

Syngas produced in fuel reactor

System temperaturecontrolled by global air/fuel ratio

Air reactor(AR)

Fuel reactor(FR)

MeOx

MeOx-1

Air

N2, Ar, (O2) CO, H2, CO2, H2O

FuelGlobal air/fuel

ratio

< 1


CLR Theory (1) – Equilibrium gas composition for pure CH4 as fuel

0

10

20

30

40

50

60

70

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2Global air ratio [-]

Gas

con

cent

ratio

n [v

-%]

H2O

CO2

H2

CO

CLR CLC

FR Temperature

1123 K (850°C)S/C = 0.0Redox

system: Ni/NiO


CLR Theory (2) – Energy balance

0

10

20

30

40

50

60

70

0.0 0.5 1.0 1.5 2.0 2.5 3.0Global air

ratio

[-]

AR

coo

ling

[% o

f tot

al h

eatr

elea

se]

CLR CLC

FR Temperature

850°C15% oxygen

carrier

conversion

per loopno heat

loss

or

FR cooling

considered


Overview CLR test runs

Fuel

reactor

temperatureGlobal air/fuel

ratio

rangeAir reactor

temperature

range

Steam/carbon

ratio

at fuel

reactor

inlet1020 K (747°C) 0.46 –

1.10 1025 –

1150 K < 0.4

1176 K (903°C) 0.52 –

1.10 1180 –

1290 K < 0.4

Fuel: natural

gas from

the

grid

(> 98.6 vol.% CH4

)

Thermal fuel

power all runs: 140 –

145 kW

Oxygen-carrier

particles: Ni/NiO

on NiAl2

O4

support


CLR results (1): AR and FR exhaust gas composition at TFR = 750°C

Equlibrium gas composition from fuel reactor (except forincomplete CH4 conversion at high global air/fuel ratio)

air to fuel ratio [-]0.4 0.6 0.8 1.0 1.2

gas

conc

entra

tion

[vol

%]

0

15

30

45

60

0

15

30

45

60

H2

CO2

COCH4

TFR ~747°CH2O

air to fuel ratio [-]0.4 0.6 0.8 1.0 1.2

gas

conc

entra

tion

[vol

%]

0

1

2

3

4

5

6

7

8

0

1

2

3

4

5

6

7

8O2

Ar

TFR ~747°C

H2O

Pröll, T., Bolhàr-Nordenkampf

J., Kolbitsch, P., Hofbauer, H., "Syngas

and a separate nitrogen/argon stream via chemical looping reforming –

a 140 kW pilot plant study", submitted

to Fuel, 2009.


CLR results (2): AR and FR exhaust gas composition at TFR = 900°C

air to fuel ratio [-]0.4 0.6 0.8 1.0 1.2

gas

conc

entra

tion

[vol

%]

0

15

30

45

60

75

0

15

30

45

60

75

H2

CO2

CO

CH4

TFR ~903°C

H2O

air to fuel ratio [-]0.4 0.6 0.8 1.0 1.2

gas

conc

entra

tion

[vol

%]

0

1

2

3

4

5

6

0

1

2

3

4

5

6

O2

Ar

TFR ~903°CH2O

Equilibrium composition from fuel reactorOxygen in the air reactor is completely absorbed for global air/fuel ratios smaller than 1.

Pröll, T., Bolhàr-Nordenkampf

J., Kolbitsch, P., Hofbauer, H., "Syngas

and a separate nitrogen/argon stream via chemical looping reforming –

a 140 kW pilot plant study", submitted

to Fuel, 2009.


CLR results (3): Oxygen absorption in AR vs. AR temperature

0.00

0.02

0.04

0.06

0.08

700 800 900 1000Air reactor mean operating temperature [°C]

O2 c

onte

nt in

AR

exh

aust

[v/v

db]

T AR = T FR = 900°Ca/f ratio 1.0 and 1.1

T AR = 800°Ca/f ratio 1.0 and 1.1


Conclusions CLR

Results with the oxygen carrier used for air/fuel ratios between 0.4 and 0.7 and steam/carbon ratios larger than 0.4:

→ the fuel reactor exhaust gas is in equilibrium→ the air reactor exhaust gas is free of oxygen→ no carbon is lost to the air reactor (no coking)

Process allows for coupled production of syngas and a O2-free stream of N2 and Ar


Outlook on demonstration

CLC state

of the

artfor

gaseous

fuelsat atmospheric

pressure

pressurized

CLCfor

GT-CCCLC for

coal

special

applications

economically

relevant only

at very

large scale

and if

CO2

infrastructure

is

present

industrial

steam

generationCLR for

H2

etc. coupled

productionstranded

natural

gas utilizationrese

arch

requ

ired

rese

arch

requ

ired


Acknowledgement

Core Partners:→ Chalmers University

of

Technology

→ CSIC Zaragoza→ Shell, BP (CCP Phase II)→ Alstom

Power

France

Funding through EC-FP6 Projects:→ CLC GAS POWER (2006-2008)→ CACHET (2006-2009)

chemical looping combustion and reforming at a 120 kw ... septiembre/c32.pdf · →thermodynamic...

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