Enhancing hydrogen yield in methane steam reforming with

CaO-Ca12Al14O33 loopingC.S. Martavaltzi, E.S. Korkakaki, E.P. Pampaka, A.A. Lemonidou

Aristotle University of Thessaloniki, Chemical Engineering DepartmentLaboratory of Petrochemical Technology

GR-54124 Thessaloniki, Greece

I. INTRODUCTION

CaCO3

CaO

H2, H2O(minor quantities of

CO, CH4, CO2)

CH4, H2O N2

SpentSorbent

FreshSorbent

Re

ge

ne

rato

r

Sorption Enhanced Reforming

• Single-Step (Lower Capital Cost)

• Higher methane conversion

• Higher H2 selectivity

• Lower CO & CO2 concentrations

• Lower Operating Temperatures

• Effective method for CO2 separation

II. THERMODYNAMICS says GO FOR IT!!!

400 500 600 700 800 9000

10

20

30

40

50

60

70

80

90

100

Temperature, o

C

CH4 SER

CH4 SR

CaO/CH4: 1

P: 1 atm

H2O/CH

4:3

CO2 SER

CO SER

H2 i

n t

he r

ea

cto

r o

utl

et,

%

H2 SER

H2 SR

CO SR

CO2 SR

0

5

10

15

20

25

30

CO

2 , CO

& C

H4 in

the r

ea

cto

r o

utle

t, %

IV2. 1st Sorption-Reforming Cycle

IV. EXPERIMENTAL RESULTS & DISCUSSION

IV1. Experimental Conditions

V. CONCLUSIONS

50

55

60

65

70

75

80

85

90

95

100

deso

rptio

ndes

orp

tion

sorpion

reforming

postbreakthroughTotal duration: 60 h

13th

cycle3rd cycle

H2 i

n t

he r

ea

cto

r o

utl

et

%

1st cycle

prebreakthrough

500

600

700

800

900

1000

1100

1200

Tem

pera

ture,

οC

• The new material CaO-Ca12Al14O33 acts effectively as a sorbent material

• Methane conversion, higher than 93% can be succeeded at the lowtemperature of 650oC

• The concentration of hydrogen in the reactor’s outlet can reach 93%

•The material CaO-Ca12Al14O33 showed a high stability after 60 hours of testing incritical conditions

• Only some of the external surface sorption sites transformed to less accessibleones

III. SCOPE OF THIS STUDY

IV3. Long-term SER experiments

•Methane conversion > 93%

•CO2<2-3%, CO < 3-4% and H2>93%

• SER experiments proved theefficiency of the sorbent and itsenhancing effect on CH4 conversion

•67% less CO2 emitted compared toconventional steam reforming (1st cycle)

• SER process increased hydrogenpurity and reduced the number ofnecessary downstream processing steps

• Higher hydrogen content of the SERreactor effluent stream leads to 94%hydrogen yield instead of 84% in SRequilibrium

• Slow kinetics of CO2 fixing on CaO-Ca12Al14O33 at temperatures lower than650oC

• 18% lower reaction rate whentemperature decreases from 650oC to550oC.

• Methane conversion, decreases from95% to 72%

• Minor differences in H2, CO and CO2

concentration profiles of the 1st and the 13th

cycle

• Sorption capacity of CaO-Ca12Al14O33 was 55%and 49% at the 1st and 13th cycle respectively

• Reduced duration of prebreakthrough periodand increased breakthrough time

•Transformation of some external surfacesorption sites to less accessible ones

The continuous but complex multi-step SteamReforming (SR) process can be replaced by a muchsimpler single-step process which employs a bedpacked with an admixture of catalyst and sorbentfor the selective removal of CO2. The latter is knownas sorption-enhanced reforming (SER) in which thehighly exothermic carbonation reaction of thesorbent is included in the reaction scheme.

Re

form

er

500 550 600 650 70050

55

60

65

70

75

80

85

90

95

100

postbreakthrough

prebreakthrough

Temperature, oC

Meth

an

e c

on

versi

on

, %

SERequil

SReq

uil

0

5

10

15

prebreakthrough

CO

2 in r

ea

cto

r o

utle

t, %CO

in

rea

cto

r o

utl

et,

%

postbreakthrough

1st cycle 3rd cycle 13th cycle0

5

10

15

Total experimental duration: 60 h

CH4 + H2O CO + 3H2 Steam Reforming

CO + H2O CO2 + H2 Water Gas Shift

CO2+CaO CaCO3 Sorption of CO2

2nd Network Meeting on High Temperature Solid Looping Cycles, September 15-17, Alkmaar

REFERENCES[1] C.S. Martavaltzi, A.A. Lemonidou, Ind. Eng. Chem. Res.47 (2008) 9537.

[2] C.S. Martavaltzi, A.A. Lemonidou, Microporous Mesoporous Mater. 110 (2008) 119.

[3] C.S. Martavaltzi, E.P. Pampaka, Energy Fuels 24 (2010) 2589.[4] C.S. Martavaltzi, T.D. Pefkos, IECR DOI:10.1021/ie1002284

Evaluation of a new sorbent material, CaO-Ca12Al14O33, for hydrogen production viaSorption Enhanced Steam Reforming throughmultiple cycles of sorption-desorption

0 50 100 150 200

60

65

70

75

80

85

90

95

100

Time, min

H2 i

n t

he r

ea

cto

r o

utl

et,

%

0

5

10

15

20

25

30

35

40

T=650oC

P=1atm

H2O/CH

4=3.4

3g CaO-CaAl

1.5g Catalyst

CO

, CO

2 in th

e r

ea

cto

r o

utle

t, %

H2

CO2

CO

0

20

40

60

80

100

120

140

%

H2 y

ield

Con

cen

trati

on

H2

Meth

an

e c

on

versi

on

SR

SER/CaO-Ca12

Al14

O33

0,0

0,5

1,0

1,5

2,0

prebreakthrough period

breakthrough period

No

rma

lize

d T

ime

1st cycle 3rd cycle 13th cycle

Sorption Desorption

• 650 oC• 1 atm• 1.5 gr industrial Ni catalyst• 3 gr sorbent material• H2O/CH4= 3.4 • CH4: 11 cm3/min

• 850 oC• He: 100 cm3/min