C.S. Martavaltzi, E.S. Korkakaki, E.P. Pampaka, A.A ... · CH 4 SR CaO/CH 4: 1 P: 1 atm H 2 O/CH...
Transcript of C.S. Martavaltzi, E.S. Korkakaki, E.P. Pampaka, A.A ... · CH 4 SR CaO/CH 4: 1 P: 1 atm H 2 O/CH...
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!!!
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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
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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
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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
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• 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
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Temperature, oC
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an
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SReq
uil
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CO
2 in r
ea
cto
r o
utle
t, %CO
in
rea
cto
r o
utl
et,
%
postbreakthrough
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5
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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
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Time, min
H2 i
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%
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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
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%
H2 y
ield
Con
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H2
Meth
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on
versi
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SR
SER/CaO-Ca12
Al14
O33
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prebreakthrough period
breakthrough period
No
rma
lize
d T
ime
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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