Prereformer Catalyst
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Transcript of Prereformer Catalyst
Research I Technology I Catalysts
Prereforming
Leif Storgaard
� Prereforming was developed back in the 60’es
especially for town’s gas plants
� The technology disappeared in the 70’es when town gas
was replaced with natural gas
� Topsøe re-invented the technology in the 90’es
� Today more than 100 plants operate with prereformer
� Topsøe prereforming catalyst is installed in about 70 %
of all prereformers
History
Feed from HDS
Process steam
Prereformer
Waste heat channel
Tubularreformer
H2O (optional)
Typical installation of a prereformer
� Increase plant capacity
� Lower energy consumption
� No risk for carbon formation in tubular reformer
� Longer life time of tubes and catalyst in reformer
� Operate at lower steam to carbon ratio
� Operate on multiple feedstocks
� Longer life time of LTS catalyst
Why install a prereformer ?
∆H
CnHm + nH2O ⇔ nCO + H2 (694 kJ/mol
for C4H10)
CO + H2O ⇔ CO2 + H2 (-41 kJ/mol)
CO + 3H2 ⇔ H2O + CH4 (-206 kJ/mol)
°298
)2
m(n +
Prereforming reactions
400
450
500
550
0 20 40 60 80 100
Distance in bed, %
Be
d t
em
pe
ratu
re,
°C
Naturel gas LPG Naphtha
Temperature profiles in prereformer with
different feedstocks
0 20 40 60 80 100
Dis tance in Bed, %
430
440
450
460
470
480
490
Be
d t
em
pe
ratu
re,
°C
3 We e ks
1 2 M o n th s
2 2 M o n th s
4 5 M o n th s
5 9 M o n th s
Temperature profiles in natural gas prereformer using
Topsøe prereforming catalyst
� The prereforming catalyst deactivates mainly due to
sulphur poisoning
� Topsøe have developed a method to evaluate the
deactivation rate of the prereformer
(Z90 method)
� Based on Z90 method the remaining catalyst life time can
be estimated
� Based on Z90 method one get a quick warning if sulphur
leakage from HDS should increase
Evaluation of prereformer performance
450
470
490
510
0 20 40 60 80 100
Bed volume [%]
Temperature [°C
]
Measured temperatures
T90
Z90
90% of ∆Tmax
∆Tmax
maxin90 T9.0TT ∆∆∆∆××××−−−−====
Graphical deactivation plot – the Z90 method
0
10
20
30
40
50
60
70
80
90
0 10000 20000 30000 40000 50000
Operating Time, Hours
Graphical deactivation plot – the Z90 method
470
475
480
485
490
495
0 10 20 30 40 50 60 70 80 90 100
Bed height, %
TExit
TMin
Z90
T90
Temperature profile for the prereformer
at a naphtha-based plant
Graphical Deactivation Plot - Z90 Method
0
20
40
60
80
100
Time
Z90, %
Excessive sulphur poisoning Z90 plot
Operation
� The prereforming catalyst should be kept reduced
during shut down /start up
1. If the catalyst is oxidized some of the sulphur picked up
on the catalyst in the top will be released
2. This sulphur will be picked up by the catalyst further
down in the bed
3. The overall catalyst activity will decrease when the
sulphur is distributed to a larger part of the bed
Key parameters for prereforming catalysts
� Activity
� Sintering (ageing)
� Carbon resistance
� Sulphur tolerance
� Resistance to gum formation
� Mechanical stability
� Pressure drop
� During development of the new AR-401 catalyst the key
parameters have been optimized
� We have used new techniques to optimize the catalyst
� Compared to AR-30, the surface area of AR-401 has
been increased while maintaining the mechanical
strength
New prereforming catalyst AR-401
Total surface area of Singapore
10 m3 AR-401 =
Surface area
� The sintering rate (ageing) has been investigated in the
electronic microscope to find the optimum composition of
the catalyst that minimize sintering
Sintering
Sehested et al. J. Catalysis vol. 223 (2004)
Particle migration
From Science to Proven Technology From Science to Proven Technology –– by Brian Munchby Brian Munch
Sintering
AR-401 other features
� AR-401is delivered pre-reduced →
no reduction during start up
� As delivered AR-401 is stable in air →
loading do not require inert atmosphere
� AR-401 can tolerate exposure to condensing steam
Thank you for your attention