Background - CO2 Capture

Attrition Evaluation of Oxygen-Carriers in Chemical Looping Systems Srivats Srinivasachar and Teagan Nelson

Envergex LLC

Johannes Van der Waat, Harry Feilen, Daniel Laudal, Michael Mann, and Steven Benson Institute for Energy Studies, University of North Dakota

Chemical-Looping-Combustion (CLC) is an innovative power generation technology for carbon capture at a lower cost and higher efficiency than state-of-the-art

• Near-pure CO2 stream produced without using oxygen from air separation • Solid oxygen-carrier (OC) used to provide oxygen to fuel • Oxygen-depleted solids regenerated separately in air • Solid oxygen carriers undergo attrition and loss of reactivity over time • Loss due to attrition and loss of reactivity creates significant operating cost burden

Project Objectives and Approach Methodology Objectives • Address critical element of CLC - loss of OC due to attrition/reactivity degradation • Evaluate attrition characteristics of oxygen carrier materials under high temperature,

reacting conditions to establish correlations between process parameters Methodology • Basis - existing standard, (ASTM D5757), used for determining attrition characteristics

of powdered catalysts by air jets • Incorporate modifications to attain test protocol more representative of chemical

looping process conditions

Experimental Setup

Temperature 800-1000°C Oxidation Composition 90% N2 , 10% O2 Oxidation Cycle Time 4 minutes Purge Composition 100% N2 Purge Cycle Time 2 minutes Reduction Composition 95% N2 , 5% H2 /CO/CO2

Reduction Cycle Time 4 minutes Test Duration (No. Cycles) 500 minutes (~50 cycles)

Evaluated multiple oxygen carriers at baseline conditions Ilmenite (2), Hematite, Red Mud, CaSO4-

based, MnOx-ore, Engineered iron oxide Cyclic operation between reduction and

oxidation conditions Measured reduction/oxidation gas

concentrations at reactor outlet

Measure attrition rate by collecting and weighing attrited material Examine the effects of varying jet velocities on the attrition of the oxygen-carriers Evaluate use of coal as fuel for reduction step on performance of selected oxygen carriers

Evaluation Strategy

Results - Evaluation Tests Ilmenite and Calcium-Based oxygen carriers had lowest attrition rates. Iron-Based-Engineered oxygen carrier had highest rate of attrition. Hematite displayed a significant breakage event during testing; thereafter attrition rate

decreased. Red Mud and Mn-Oxide-Based materials exhibited attrition rates that were slightly increasing or

relatively stable over entire test period.

Results – Effect of Gas Composition on OC Performance

Future Work Effect of operating parameters on attrition

and reactivity will be characterized to develop knowledge database and formulate strategies for commercial test service offerings. Expansion of work to study effect of

cyclonic/impaction conditions on attrition and reactivity characteristics of Oxygen Carriers. materials.

Conclusions Methodology: effective tool to down-

select oxygen carriers based on attrition propensity and reactivity Successful coal injection tests illustrate

application of attrition setup as a valuable tool for future CLC research.

Acknowledgements Contact Details Srivats Srinivasachar, Envergex LLC Phone: (508) 347-2933; Mobile: (508) 479-3784; E-mail: srivats.srinivasachar@envergex.com

CLC reaction commenced quickly as CO and CO2 is formed immediately upon injection of lignite coal. Formation of CO2 confirms CLC reaction, as no oxygen was fed to the reactor. The oxygen carrier and steam were

sources of oxygen for reaction

↑Ilmenite- attrition, under differing reducing gas compositions

↑Ilmenite- reactivity performance

Project Manager: John M. Rockey, DOE STTR; DE-SC0011984

Results – Effect of Manufacturing Conditions

Results – OC Performance with Solid Fuel Combustion

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

698 703 708 713 718 723

Gas

Con

cent

ratio

n (%

Vol

ume)

Time (min.)

% CO2% CO% H2% CH4% O2

Reduction (Coal Injection)

Oxidation

Degree of reduction affected attrition and reactivity performance • Increasing CO/H2 concentration resulted in better fuel utilization indicating higher reduced

state of OC • Increasing CO/H2 concentration caused agglomeration (20% - 30% concentration) • Degree of reduction critically important

Reactivity of different OC’s at same test conditions

0%10%20%30%40%50%60%70%80%90%

100%

0 1 2 3 4 5 6

Cum

ulat

ive

CO2 r

elea

se p

er to

tal

avai

labl

e ca

rbon

Time (min.)

Fe_3 @ 820 °C

102030

Stable reactivity

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 100 200 300 400 500 600

Attr

ition

Rat

e (%

/hou

r-w

eigh

t/in

itial

w

eigh

t)

Time (min.)

OC sintered at 1300 °COC sintered at 1250 °C

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0 200 400 600 800

Attr

ition

Rat

e (%

/hou

r-w

eigh

t/in

itial

w

eigh

t)

Time (min.)

10% CO and 10% H220% CO and 20% H230% CO and 30% H2

↓ Ilmenite - PSD of pre- and post-run samples

Effect of sintering on OC performance • The attrition rate between the two samples exhibited similar trends • Manufacturing (Sintering) at higher temperature caused a decrease in reactivity

↑Sintered Samples-attrition ↑Sintered Samples-reactivity

↓ Attrition- different OC’s

↑ Fe-based carrier under coal injection ↕ Fe-based carrier under coal injection

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

10% CO and 10% H2 20% CO and 20% H2 30% CO and 30% H2

Post

/Pre

Run

Size

Rat

io

0

1

2

3

4

5

6

0 100 200 300 400 500

Attr

ition

Rat

e (%

/hou

r-w

eigh

t/in

itial

wei

ght)

Time (min.)

Fe_5.2

Fe_4.2

Fe_3

0%10%20%30%40%50%60%70%80%90%

100%

0 1 2 3 4 5 6

Cum

ulat

ive

CO2 r

elea

se p

er to

tal

avai

labl

e ca

rbon

Time (min.)

Fe_5.2 @ 970 °C

104055Decreasing

reactivity

0%10%20%30%40%50%60%70%80%90%

100%

0 1 2 3 4 5 6

Cum

ulat

ive

CO2 r

elea

se p

er to

tal

avai

labl

e ca

rbon

Time (min.)

Fe_4.2 @ 970 °C

104051

Increasing reactivity

97% -> 89%

98% -> 46%

99% -> 30%

78% -> 32% 88% -> 16%

89% -> 5%

0102030405060708090

100

10% 20% 30%

Aver

age

Gas C

onve

rsio

n pe

r cyc

le

(%/c

ycle

)

Reducing Gas Composition

H2CO

Starting and end conversion per cycle

↓ Ilmenite - Average Gas Conversion per cycle

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 100 200 300 400 500 600

(Act

ual f

uel c

onsu

mpt

ion)

/(Th

eore

tical

fu

el c

onsu

mpt

ion)

Time (min.)

30% CO and 30% H220% CO and 20% H210% CO and 10% H2

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50

Fuel

con

vers

ion

(%)

Time (min.)

H2 (Sintered at 1250 °C)H2 (Sintered at 1300 °C)CO (Sintered at 1250 °C)CO (Sintered at 1300 °C)