Improvements to water gas shift process
John Brightling Johnson Matthey
W
ith a growing population supplies of
natural resources are under ever-increasing pressure, their sustainable
use has never been higher on the agenda. Against
this backdrop, Johnson Matthey (JM) seeks to
improve the efficiency, effectiveness and sustainable impact of their products, enabling JM customers to achieve high productivity by making
more for less.
Through a new patented solution JM has used
expertise in purification science and engineering
skills to develop an innovative new shift product
which extends LTS life allowing ammonia plants
to increase their process reliability and production efficiency.
Introduction
Water gas shift reaction
The water gas shift reaction plays a major role in
ammonia plant design and operation. Good performance of the shift catalysts, and attainment of
a close approach to equilibrium thus minimising
the CO slip from the catalyst system which is critical to the efficient and economic operation of the
plant and ensures maximum hydrogen production from the hydrocarbon feedstock. The water
gas shift or shift reaction (1) is highlighted below.
CO + H2O ⇔ CO2 + H2 (1)
The reaction is exothermic and high conversions are favoured by low temperature and a
high steam ratio. Ammonia plants usually operate a two-stage system – a High Temperature
Shift (HTS) followed by a Low Temperature Shift
(LTS) – with a suitable form of inter-bed cooling,
as in Figure 1.
The choice of shift catalyst and how they operate are vital to the economy and efficiency of an
ammonia plant. It is essential that the shift catalysts produce the lowest possible exit concentration of carbon monoxide in a stable and HTS catalyst duty
predictable manner. The catalysts need to be The HTS is a Fe-Cu-Cr catalyst that is relatively
able to withstand the challenges presented in real insensitive to poisons. HTS catalysts have lower
plant operations for an increasing period of years
activity and must be operated at higher temJohn Brightling
between planned shutdowns.
peratures (typically 350-470°C) the gas stream
The water gas shift reaction and attributes for leaving the HTS reactor therefore contains a subThe
is exothermic
andinhigh
favouredamount
by low of
temperature
and a high(usually
steam ratio.
goodreaction
catalysts
are discussed
thisconversions
paper, plus arestantial
carbon monoxide
Ammonia
plants usually
a two-stage
system2-3%).
– a High Temperature Shift (HTS) followed by a Low
an introduction
to newoperate
purification
technology
Temperature
Shift
(LTS)
–
with
a
suitable
form
of
inter-bed
cooling,
as insits
Figure
1.
developed for use in the HTS reactor to further
The HTS
catalyst
immediately
downstream
improve the performance of a LTS catalyst.
of high temperature reforming systems and heat
Figure 1 – Typical arrangement of WGS system in an ammonia plant
Figure 1 Typical arrangement of WGS system in an ammonia plant
HTS catalyst duty
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November 2019 1
The HTS is a Fe-Cu-Cr catalyst that is relatively insensitive to poisons. HTS catalysts have lower activity
and must be operated at higher temperatures (typically 350-470oC) the gas stream leaving the HTS reactor
mpact of this on HTS can be mitigated using both high voidage inert hold-down media and a
Improvements to Water Gas Shift Process
shaped HTS pellet such as KATALCO 71-5F. (Figure 2).
Figure 2 – KATALCO 71-5F shaped HTS
Figure 2 KATALCO 71-5F shaped HTS
TALCO 71-5Frecovery
offers 12%(boilers
lower pressure
drop than the conventional
and superheaters).
The heat tablet with increased
3 voidage
– High
inert DYPOR
e shape offersrecovery
additionalequipment
voidage to is
accommodate
any
deposits
that may
foulFigure
HTS
bed voidage
highly stressed which can
Figure
3the
High
inert DYPOR
media media
rate of any resultant
pressure
drop
increase
on
the
HTS
from
deposits.
cause failure leading to leakages and deposits
onto the HTS bed. The HTS is the first catalyst sure drop solution. STREAMLINE was origBelow the HTS bed the use of similar inert media is well established in shift reactors as Joh
so can 607
be can
fouled
by refractory
inally
to several high
f the HTS bedbed
highdownstream
voidage inert DYPOR
be used
protect the
top
of
a developed
catalystSTREAMLINE
bed in response
STREAMLINE
lowtopressure
drop
solution.
was
originally developed
in resp
or
metal
dusting
debris
that
may
be
emitted
from
temperature
(HT)
and
low
temperature
(LT)
uring boiler solids and by preventing the
impingement
of
liquid
droplets
onto
the
catalyst
itself.
high temperature (HT) and low temperature (LT) shift reactors exhibiting high press
high temperature
is solution as the
SHIFTSHIELD,
Figure 3. recovery equipment. The shift reactors exhibiting high pressure drops. On
discoveredinvestigation
that a high portion
the vessel that
pressure
drop
was associate
fouling impact of thisinvestigation
on HTS canit was
be mitigated
it wasofdiscovered
a high
porImprovements
to
Water
Gas
Shift
Process
using both high voidage
inert
media
of thebyvessel
pressure
drop wasflow
associated
around
thehold-down
collector. This
was tion
confirmed
detailed
computational
modelling. (Figure 4
and a high voidage shaped HTS pellet such as with the area around the collector. This was conKATALCO 71-5F. (Figure 2).
firmed by detailed computational flow modelling.
Shaped KATALCO 71-5F offers 12% lower (Figure 4).
pressure drop than the conventional tablet with
The specific size grades of DYPOR, used as a
Nitrogen + Syngas
International
& Exhibition
(Berlin 4 - media,
7 March 2019)
increased strength.
The 2019
shape
offersConference
additional
support
vary depending on the vessel convoidage to accommodate any deposits that may figuration and particle size of material being supfoul the HTS bed lowering the rate of any resultant ported. JM have a proprietary STREAMLINE
pressure drop increase on the HTS from deposits.
software program which is configured for a full
Also on top of the HTS bed high voidage inert range of vessel collector designs. Figure 5 shows
DYPOR 607 can be used to protect the top of a a STREAMLINE model of a vessel with a dished
– High
voidage
inert DYPOR
media solids and
catalyst Figure
bed 3by
both
capturing
boiler
bottom collector, along with plant data showing
by preventing the impingement of liquid droplets the 60% reduction in pressure drop that resulted
onto
the catalyst
itself.
marketin this
solution
from Matthey’s
the deployment of STREAMLINE on this
HTS bed the use
of similar
inert media
is wellJM
established
shift reactors
as Johnson
as SHIFTSHIELD,
Figure 3.was originally developed in response
vessel.to several
LINE low pressure
drop solution. STREAMLINE
perature (HT) and
low temperature
On
Below
the HTS (LT)
bed shift
the reactors
use of exhibiting
similar high
inertpressure
Androps.
enhancement
to STREAMLINE technolon it was discovered
that
a
high
portion
of
the
vessel
pressure
drop
was
associated
with
the
area
media is well established in shift reactors as ogy is now available as discussed later, utilise collector. ThisJohnson
was confirmed
by detailed STREAMLINE
computational flow modelling.
(Figureing
4). PURASPEC 2272 as a high voidage support
Matthey’s
low presmedia, which also provides LTS protection from
Figure 4: STREAMLINE
flow modelling of shift reactor
chloride
poisons.
LTS used as a support media, vary depending on the vess
The specific size grades of DYPOR,
The efficiency of ammonia plants depends critand particle size of material being
supported.
JM have
proprietary
STREAMLINE
ically
on the ability
of a
the
LTS catalyst
to con- software
is configured for a full range of vessel
designs.
a every
STREAMLINE m
vert thecollector
maximum
amountFigure
of CO 5toshows
H2. For
with a dished bottom collector,molecule
along with
plant
data
showing
the
60%
reduction
in pres
of CO passing through the LTS there
is
only the loss in
resulted from the deployment ofnot
STREAMLINE
onproduction
this vessel.of H2 via equation
1, but also a further loss of three molecules of H2
in the methanation of CO, equation 2, and further loss when this extra methane is purged from
the synthesis loop.
Figure 4: STREAMLINE flow modelling of shift reactor
Figure 4 STREAMLINE flow modelling of shift reactor
CO + 3H2O ⇔ CH4 + H2O
fic size grades of DYPOR, used as a support media, vary depending on the vessel configuration
e size of material being supported. JM have a proprietary STREAMLINE software program which
2 November
2019collector designs. Figure 5 shows a STREAMLINE model of a vessel
ed for a full range
of vessel
hed bottom collector, along with plant data showing the 60% reduction in pressure drop that
om the deployment of STREAMLINE on this vessel.
(2)
www.digitalrefining.com/article/1002381
John Brightling
Shift Reactor
Pressure Drop kg/cm2
2
1.5
1
0.5
0
Standard
STREAMLINE
Figure flow
5: Case
study STREAMLINE
Figure 5 Case study STREAMLINE
simulation
and results flow simulation and results
LTS catalyst composition
vice, the active Cu phase and catalyst structure
An enhancement
to STREAMLINE technology is now available as discussed later, utilising PURASPEC
A catalyst is designed to increase the rate of reac- should also be unaffected, as far as possible, by
2272tion
as but
a high
support
media, which also
provides
LTS
protection
fromprocess
chloride
doesvoidage
not change
the thermodynamic
equitraces
of poisons
in the
gaspoisons.
stream.
librium concentration of reactants and products
The properties of the LTS catalyst are critically
for the actual operating conditions. The catalyst dependent upon the formulation and manufacLTSmust, therefore be formulated for long-term reli- turing process rather than on the bulk chemical
able operation at, or near, equilibrium conditions.
analysis. The importance of the correct control of
LTS catalyst
is copper
(Cu)
distributed
on on
a the
formulation
conditions
are key
The efficiency
of ammonia
plants
depends
critically
ability of theand
LTSpreparation
catalyst to convert
the maximum
mixed support of zinc oxide (ZnO) and alumina in obtaining the correct LTS structure to give a
amount of CO to H2. For every molecule of CO passing through the LTS there is not only the loss in
(Al2O3). The LTS catalyst is supplied as a mix- catalyst that offers long-term stable activity and
production
of H2 via
equation 1, but also a further loss of three molecules of H in the methanation of CO,
ture of oxides,
and the copper oxide (CuO) is in a mechanical properties, 2 thus avoiding pressure
equation
and
further
loss and
whenquickly
this extra
methane
from the synthesis loop.
form 2,
that
can
be easily
reduced
into is purged
drop increase.
the active form. The Cu crystallites
formed in this
Improvements
to WaterEnergy-dispersive
Gas Shift Processx-ray spectroscopy (EDX) is
way must not sinter and
COlose
+ activity
3H2O during
 ser-CHan
H2O technique
(2)used by JM for the ele4 +analytical
LTS catalyst composition
Al
A catalyst is designed to increase the rate of reaction but does not change the thermodynamic equilibrium
concentration of reactants and products for the actual operating conditions. The catalyst must, therefore be
formulated for long-term reliable operation at, or near, equilibrium conditions.
LTS catalyst is copper (Cu) distributed on a mixed support of zinc oxide (ZnO) and alumina (Al2O3). The LTS
catalyst is supplied as a mixture of oxides, and the copper oxide (CuO) is in a form that can be easily and
Zn
Cu in this way must not
quickly reduced into the active form. The Cu crystallites formed
sinter and lose activity
during service, the active Cu phase and catalyst structure should also be unaffected, as far as possible, by
traces of poisons in the process gas stream.
The properties of the LTS catalyst are critically dependent upon the formulation and manufacturing process
rather than on the bulk chemical analysis. The importance of the correct control of formulation and
preparation conditions are key in obtaining the correct LTS structure to give a catalyst that offers long-term
Figure
EDX analysis
KATALCO
83-3X showing
elemental
of catalyst structure
Figure
6 EDX and
analysis
of6:KATALCO
83-3Xofshowing
mapping
of catalyst
structure
stable
activity
mechanical
properties,
thuselemental
avoiding
pressure
dropmapping
increase.
To achieve a longx-ray
and active
life the copper
(red) must used
be small
separated
from
Energy-dispersive
spectroscopy
(EDX) metal
is an crystallites
analytical technique
by and
JM well
for the
elemental
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November 2019 3To
each
other
by
even
smaller,
yet
thermally
stable,
zinc/alumina
refractory
oxide
crystals
(blue/green).
analysis or chemical characterisation of catalysts. It relies on an interaction of some source
of x-9 meter).
the necessary
catalytic
behaviour the scale
of this are
science
measured
nano-meters
rayobtain
excitation
and a sample,
its characterisation
capabilities
due inis large
part tointhe
fundamental(10
principle
Bulkeach
analysis
of the LTS
cannot
be used
as a basis
of assessment
of LTSoncatalyst
that
element
has catalyst
a unique
atomic
structure
allowing
a uniqueor comparison
set of peaks
its
John Brightling
Strength (Kgf)
resistance, stability, selectivity and activity that is
manufactured to achieve a
high dispersion of Cu crystallites within the ZnO/
Al2O3 structure. The ZnO/
Al2O3 refractory crystallites add strength to the
catalyst while providing a
stable support maintaining
the high dispersion of the
active Cu sites and therefore
inhibit the Cu crystallites
from sintering thus maintaining activity and life.
Figure 7Figure
Increasing
poisons
resistance
or or
activity
onLTS
LTSperformance
performance
After stabilising in-ser7: Increasing
poisons
resistance
activity––effect
effect on
vice, the LTS catalyst needs
mental analysis or chemical characterisation of to display stable performance throughout its
If a level of 0.3% CO slip is considered as being end of run (EOR) condition, then, as can be seen from
catalysts. It relies on an interaction of some working life – meaning uniform activity, retained
Figure 7 from a base case of current LTS technology, - increasing LTS activity to 150% could increase
source of x- ray excitation and a sample, its char- strength and good capacity for poisons. The relservice life to 6 years whereas a 150% increase in poisons resistance extends the life to over 7 years.
acterisation capabilities are due in large part to ative effects of increasing poisons resistance and
theLTS
fundamental
Operation of
catalyst principle that each element has activity of LTS are shown in Figure 7.
If a level of 0.3% CO slip is considered as being
a unique atomic structure allowing a unique set
of peaks on its electromagnetic emission spec- end of run (EOR) condition, then, as can be seen
Considering what
understanding
catalyst
science
and LTS composition
means 7in from
operation,
typical
from Figure
a base
case of current LTS
trum.this
Figure
6 shows ofthe
structure
of KATALCO
use of LTS catalyst
comprises
of
three
stages:
technology, increasing LTS activity to 150% could
83-3X catalyst using EDX.
To achieve a long and active life the copper increase service life to 6 years whereas a 150%
metal
crystallites
must be without
small incident
and well increase in poisons resistance extends the life to
• catalyst
is loaded,
reduced(red)
and started-up
separated from each other by even smaller, yet over 7 years.
• catalyst is operated with trace levels of poisons as would be expected with a normally operating
thermally stable, zinc/alumina refractory oxide
purification system
crystals (blue/green). To obtain the necessary cat- Operation of LTS catalyst
• after many
of stable
at equilibrium
levelsConsidering
and low pressure
drop,
theunderstanding
catalyst
what
this
of catalyst
alytic years
behaviour
theoperation
scale ofwith
thisCO
science
is measis discharged
ured in nano-meters (10-9 meter). Bulk analysis science and LTS composition means in operation,
use ofpoisons
LTS catalyst
comprises of three
of the LTS
cannot
be used
a basis
During the operation
of ancatalyst
ammonia
plant there
are as
trips,
boiler of
leaks,typical
and catalyst
that are an
assessment
or comparison
LTS
catalyst
since
it stages:
unavoidable part
of plant operation,
and theofLTS
catalyst
must
be designed
to survive these.
yields no information on the fundamental proper- • catalyst is loaded, reduced and started-up
without incident
ties or mechanism for operation such as:
KATALCO 83-3
catalyst series have an excellent reputation of doing this. The catalyst structure retains a
• Quantity or size of the copper crystallites pro- • catalyst is operated with trace levels of poisons
high in-serviceducing
strength
which is especially critical to the operator as thisas
is the
strength of the catalyst in the
would be expected with a normally operating
catalytic action
in-service condition,
once
reduced
and
used
in
plant
conditions.
The
attached
benchmark
data shows with
purification
system
• The micro-structure for poisons resistance
in-service strengths
measured
on
reduced
catalyst
using
a
crush
machine
housed
in
an
inert
of stable operation with CO at
• The form of the alumina, which in turn affects • after many yearsatmosphere.
equilibrium levels and low pressure drop, the catthe strength and stability of the catalyst.
Through this leading science JM can manage alyst is discharged
During the operation of an ammonia plant there
the formulation
and manufacture of the LTS cat15
alyst with stringent controls to achieve the opti- are trips, boiler leaks, and catalyst poisons that are
mum structure balancing good activity, thermal an unavoidable part of plant operation, and the
10
stability and the ability to withstand the effect of LTS catalyst must be designed to survive these.
KATALCO 83-3 catalyst series have an excelpoisons hence enhancing life.
lent reputation of doing this. The catalyst struc5
ture retains a high in-service strength which is
Activity and life
The current formulation of KATALCO 83-3 LTS especially critical to the operator as this is the
0
catalysts is a careful balance between poisons strength of the catalyst in the in-service condiJM LTS
4 November 2019
COMP A/1
COMP A/2
COMP B/1
Fresh
In-Service
COMP B/2
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Nitrogen + Syngas 2019 International Conference & Exhibition (Berlin 4 - 7 March 2019)
in-service strengths measured on reduced catalyst using a crush machine housed in an inert atmosphe
15
Strength (Kgf)
tion, once reduced and
used in plant conditions. The attached
benchmark
data
shows with in-service
strengths
measured
on reduced catalyst
using a crush machine
housed in an inert
atmosphere.
Fresh In-Service
10
5
0
JM LTS
COMP A/1
COMP A/2
COMP B/1
Fresh
In-Service
COMP B/2
These results show
how for all LTS cat- Figure 8 Relative strengths of LTS catalyst for both fresh and in-service conditions
alysts 6the
reduced
Nitrogen + Syngas 2019 International Conference & Exhibition (Berlin 4 - 7 March
This has the economic benefit of reducing the
strength of pellets lower than for fresh oxidic. For
JM LTS the in-service pellet strength is higher cost of nitrogen or natural gas used during the
than competitive LTS pellets. This increased LTS catalysts reduction, however, the main benestrength helps provide stable performance with- fit is that it provides a larger operational envelope
for catalyst reduction without risk of achievout increasing in-service pressure drop.
A further operational difference from the struc- ing a low catalyst activity. During LTS reductural science of KATALCO 83-3 catalysts is the tion, monitoring of the gas composition is often
tolerance to catalyst reduction process condi- undertaken with temporary instrumentation and
tions. The catalyst reduction itself is a transient manual control of the purge flow. Therefore, a
process in which the CuO in the LTS is reduced wider operating envelope within the period of
to the active Cu metal, often in a recirculation less than ideal control is especially useful.
loop. When a recirculating system is used there
needs to be a continuous purge from the system LTS catalyst poisons
to prevent the level of contaminants from build- The two most virulent poisons for an LTS charge
ing up within the system. The oxidic LTS catalyst are sulphur and chlorides. They are the major
contains some complex copper-zinc basic car- source of LTS deactivation. The main catalyst
bonates and these decompose during reduction poisons sources and their effects are summarised
and release carbon dioxide (CO2). The amount of in Table 1.
CO2 in the recirculating carrier gas is one of the
key parameters that determine the level of purg- Sulphur
Catalysts start to be poison whenever an impuing from the recycle loop.
There is a potential for the CO2 in the recirculat- rity in the process gas alters the surface structure
ing gas to react with oxides in the LTS catalyst and or composition of the active metal. Sulphur, which
damage its microstructure. The damage occurs is the most common of these poisons, deactivates
primarily in the support phase of the catalyst, LTS catalyst by a process of chemisorption onto the
resulting in a weakening of the catalyst pellets. active copper surface followed by crystallite growth.
Hydrogen sulphide (H2S) can be absorbed as a
This is often observed as a higher than expected
LTS pressure drop as soon as the plant is started layer onto active Cu surface at much lower partial
up, which then increases rapidly during ongo- pressures than required for bulk sulphides. As
ing operation. Therefore, limits on the CO2 partial such Cu in LTS catalyst is very active for absorbpressure have been applied during some LTS cata- ing a surface layer of H2S if present in the reactlyst reductions, with a figure of circa 1bara (15psia) ing process gas. However, since thermodynamic
being typical for some products. By optimising the data predicts H2S will react preferentially with
catalyst formulation, of KATALCO 83-3 series JM ZnO rather than Cu it essential that an LTS catahave engineered a rugged stable support phase for lyst is designed such that sulphur is rapidly transthe active sites, meaning it is an LTS catalyst less ferred from the active Cu metal to ZnO before the
Cu sinters.
sensitive to the level of CO2 in the reduction gas.
www.digitalrefining.com/article/1002381
November 2019 5
John
Brightling
The two most virulent poisons for an
LTS charge
are sulphur and chlorides. They are the major source of
LTS deactivation. The main catalyst poisons sources and their effects are summarised in Table 1.
surface of free ZnO present in
a catalyst. Those containing
Sulphur
Hydrocarbon feedstock
Covers active copper surface
less available ZnO can allow a
o be poison whenever anLubricating
impurity
or
oil in the process gas alters the surface structure
given quantity
of H2S to penehe active metal. Sulphur, which
is
the
most
common
of
these
poisons,
deactivates
LTS
trate deeper into the bed causAir to secondary reformer
cess of chemisorption ontoNew
theHTS
active
copper surface followed by crystallite growth.ing greater deactivation.
catalyst
Poison
Possible sources
Effect on LTS catalyst
Chloride
Steam
Promotes copper crystal growth
Chloride
Quench
wateronto active Cu surface at much lower partial pressures
de (H2S) can be absorbed as
a layer
Chloride as a poison presents
Lubricating
bulk sulphides. As such Cu in LTSoilcatalyst is very active for absorbing a surfacemore
layerofofa challenge in the LTS
reactor
to secondary teformer
n the reacting process gas.Air However,
since thermodynamic data predicts H2S will
reactbecause of the low
h ZnO rather than Cu it essential that an LTS catalyst is designed such that sulphur melting
is rapidlypoint and high solubilTable 1 Main LTS
poisons
sources
andandtheir
effects ities in water of zinc, copper chlorides. Chloride
Tablecatalyst
1before
– Main LTS
catalyst
sources
their effects
the active Cu
metal to ZnO
the
Cupoisons
sinters.
can be redistributed through the catalyst bed
by dissolution in7 condensed water or by vapour
phase transfer of volatile chloride. Consequently,
the absorption profile for chloride in the catalyst bed is not as stable as for sulphur and chloride can be distributed deeper into the bed. So,
although the levels of chloride reaching the LTS
bed are generally lower than sulphur the damage
can be more harmful.
The levels of S and Cl vary from plant to plant
depending on the prevalent conditions of poisons. Ranges seen on inlet LTS catalyst samples
Figure 9 - Schematic mechanism for S capture within LTS
taken at the top of the bed over a wide range of
Figure 9 Schematic mechanism for S capture within LTS
over 150 plant samples, are shown in Figure 10.
formulated
there is an
excess
of
High
surface coverages
ted LTS, thereInisaanwell
excess
of free LTS,
ZnO meaning
that
H2S presence
is absorbed
quickly atare often seen of both
free ZnO meaning that H2S presence is absorbed sulphur and chloride on discharged samples,
d leaving the rest of the catalyst to operate satisfactorily. Absorption capacities of around
quickly at the top of the bed leaving the rest of often above 1 wt.% at the top of the bed. A long
en measuredthein catalyst
KATALCO
83-3 series
LTS catalysts
in plant use.
The feature
Sulphurofcapacity
to operate
satisfactorily.
Absorption
standing
JM LTS technology is that it is
o the surfacecapacities
of free ZnO
present6%inwt.
a catalyst.
Those
containing
less available
ZnO of
can
of around
have been
measured
self-guarding
in terms
both S and Cl. Figure 11
antity of H2SintoKATALCO
penetrate deeper
into
the
bed
causing
greater
deactivation.
83-3 series LTS catalysts in plant shows an EPMA (electron probe micro analysis)
use. The Sulphur
capacity
relates Gas
directly
the of spent KATALCO 83-3 series LTS showing the
Improvements
to Water
ShifttoProcess
distribution of both S and Cl captured on the surface of the pellets.
As shown in Figure 10, typical
levels of chloride in spent LTS are
much
ison presents more of a challenge in the LTS reactor because of the low melting
pointlower
and level than sulphur,
however even these low Cl-levels
n water of zinc, copper chlorides. Chloride can be redistributed through the catalyst
bed by
have the potential to be much
ndensed water or by vapour phase transfer of volatile chloride. Consequently, themore
absorption
damaging, for two reasons:
e in the catalyst bed is not as stable as for sulphur and chloride can be distributed
deeper - both copper and
• Cl-solubility
, although the levels of chloride reaching the LTS bed are generally lower thanzinc
sulphur
the are soluble in water,
chloride
hence condensation on the catamore harmful.
lyst during start-up, shutdown or
normal operation can move chloand Cl vary from plant to plant depending on the prevalent conditions of poisons.
ridesRanges
further down the bed.
• Cl-induced
S catalyst samples taken at the top of the bed over a wide range of over 150 plant
samples, sintering - low levels of chlorides can have a signifiure 10.
cant effect on LTS catalyst activity
Figure 10
10: Levels
Levelsof
of Sulphur
Sulphur and
and Chloride
Figure
Chloride measured
measuredininspent
spentLTS
LTScatalysts
catalysts
since they promote sintering.
Nitrogen + Syngas 2019 International Conference & Exhibition (Berlin, 4 - 7 March 2019)
ce coverages are often seen of both sulphur and chloride on discharged samples, often above 1
November 2019
e top of the6 bed.
A long standing feature of JM LTS technology is that it is self-guardingwww.digitalrefining.com/article/1002381
in terms
nd Cl. Figure 11 shows an EPMA (electron probe micro analysis) of spent KATALCO 83-3 series
ng the distribution of both S and Cl captured on the surface of the pellets.
of both S and Cl. Figure 11 shows an EPMA (electron probe micro analysis) of spent KATALCO 83-3
LTS showing the distribution of both S and Cl captured on the surface of the pellets.
To understand why the
impact of Cl is so pronounced
the effect of temperature
on sintering of metals and
oxides should be considered.
Temperature is the dominant
factor in controlling the rate of
sintering of metallic and oxidic
species. Relationships have
John Brightling
been evolved which utilise the
melting point of theAccordingly,
material sintering rates of a metal or metal compounds are significant and very high near the Tamman
concerned to estimatetemperature;
the
magthus, the
relative
thermal
stability
materials
beoncorrelated
terms
of surface
the Tamman
Figure
11: EMPA
analysis
showing
mapping
analysis
for S can
and Cl
KATALCOin 83-3
pellet
nitude of the sintering
process Figure
EMPAlists
analysis
mapping
S and Cl on KATALCO
temperatures,
Table 11
2 below
theseshowing
for the LTS
metalsanalysis
and theirfor
compounds.
at any given temperature. The 83-3 pellet surface
Tamman temperature
is Figure
calcu- 10, typical levels of chloride in spent LTS are much lower level than sulphur, ho
As shown in
Tmp (Melting point)
TTamman ( = 0.5 Tmp ºK)
lated (in absolute
units)low
as one
even these
Cl-levelsCompound
have the potential
to be much more damaging,
for two reasons:
half of the melting point of the
ºK
ºC
ºK
ºC
metal or oxide. This gives an
Cu
1356
1083
678
405
indication of the
• temperature
Cl-solubility - both copper and zinc chloride are soluble in water, hence condensation o
at which metal or metal
oxide
893or normal operation
620
174further down the b
2
catalyst
duringCuCl
start-up,
shutdown
can447
move chlorides
atom lattices experience mobilCuCl
703
430
352
79
Cl-induced
ity, physically in• terms
of the sintering - low levels of chlorides can have a significant effect on LTS catalyst a
since they promote
CuO sintering. 1599
1326
800
527
driving forces for dissociation
and diffusion of surface atoms.
Zn
693
420
347
74
Accordingly, sintering rates
understand
why theZnO
impact of Cl is so
pronounced
the effect of1124
temperature851
on sintering of meta
2248
1975
of a metal orTo
metal
compounds
oxides
should
be
considered.
Temperature
is
the
dominant
factor
in
controlling
the
are significant and very high
ZnCl2
563
290
282
9rate of sintering of m
near the Tamman
temperature;
and oxidic
species. Relationships have been evolved which utilise the melting point of the material conc
Table 2: Melting point and Tamman temperatures for LTS metals/compounds
thus, the relative
thermalthe
stabilTable 2ofMelting
point and
Tammanat
temperatures
LTS metals/compounds
to estimate
magnitude
the sintering
process
any given for
temperature.
The Tamman tempera
ity materialscalculated
can be correlated
(in absolute units) as one half of the melting point of the metal or oxide. This gives an ind
Sintering
of LTS catalysts
is strongly
promoted
by traces
of chlorine in thewas
feed,good
which with
react at operating
in terms of the Tamman
temperatures,
Table
2 years
on-line
the performance
of the temperature
at which
metal
or
metal oxide
atom
lattices
experience
mobility,
physically
terms
temperatures
with
the
active
metal/metal
oxide
surface
to
produce
a
highly
mobile
chloride
phases.inCopper
below lists these for the LTS metals and their low CO slip (<0.2%) and the reaction exotherm
driving
forces
for
dissociation
and
diffusion
of
surface
atoms.
chlorides having a Tamman temperature
of only
79–174
to 405 °C for copper metal and zinc
compounds.
showed
little
signs°C
of compared
poisoning.
chloride
a
Tamman
temperature
of
only
9
°C
relative
to
851
°C
for
ZnO.
such the
formation of copper
Sintering of LTS catalysts is strongly proHowever, following a plant tripAswhich
resulted
and
zinc
chlorides
provide
a
mechanism
for
loss
of
activity
and
poisoning
by
sintering,
moted by traces of chlorine in the feed, which in the LTS being wetted, the CO slip increased to as shown
schematically in
Figure
react at operating temperatures
with
the12.active End of Run (EOR) conditions. Consequently, the
metal/metal oxide surface to produce a highly reaction exotherm moved much deeper into the
mobile chloride phases. Copper chlorides having bed becoming less sharp. The Key Performance
a Tamman Nitrogen
temperature
79–174°C
com-& Exhibition
Indicators
over2019)
this incident are shown in
+ Syngas of
2019only
International
Conference
(Berlin,(KPI)
4 - 7 March
pared to 405°C for copper metal and zinc chlo- Figure 13.
ride a Tamman temperature of only 9°C relative
After the wetting damage the inefficient LTS
to 851°C for ZnO. As such the formation of copper performance significantly increased production
and zinc chlorides provide a mechanism for loss costs. The plant therefore made an unplanned
of activity and poisoning by sintering, as shown shutdown to change the LTS catalyst. An estischematically in Figure 12.
mate of the production costs for this event was in
the range $1,000,000 – $5,000,000.
Case study – impact of wetting
This case study illustrates the impact a wet- New purification technology for shift reactors
Figure 12: Schematic mechanism for Cl promoted sintering of LTS
ting incident can have on LTS performance. An JM’s latest development in technology combine
ammonia plant using competitive product strat- strong purification expertise with the design of
Case study
impactbed
of wetting.
egy, including a Cl-guard
layer– (5%
depth) low pressure drop systems for shift reactors to
over the main bed catalyst. After less than two develop PURASPEC™ 2272 - an ‘adsorbing inert’.
This case study illustrates the impact a wetting incident can have on LTS performance. An ammonia plant
using competitive product strategy, including a Cl-guard layer (5% bed depth) over the main bed catalyst.
After less than two years on-line the performance was good with low CO slip (<0.2%)
and 7the reaction
www.digitalrefining.com/article/1002381
November 2019
exotherm showed little signs of poisoning.
es provide a mechanism for loss of activity and poisoning by sintering, as shown
Figure 12.
completed on its effectiveness as an Cl-guard at
typical HTS exit test conditions.
The process gas used was representative of plant
conditions H2, 55%; CO 4%, CO2, 16% and N2 25%
containing only a low level of HCl at 9ppbv.
During the test no Chloride was detected in
the exit gas. After the test was completed the
PURASPEC absorbent was recovered and analysed for C content – the inlet portion contained
330ppm similar to the level of Cl levels that would
be found at the top of the LTS bed in a similar
duration test. In long term operation within plants
that saturation capacity of PURASPEC 2272 is well
Figure
12: Schematic
mechanism
for Clfor
promoted
sintering of LTSabove 1% chloride meaning it is expected to more
Figure
12 Schematic
mechanism
Cl promoted
sintering of LTS
than match %w/w Cl capture that takes place normally within the LTS bed.
pact of wetting.PURASPEC 2272 is a low pressure drop active
adsorbent support media that replaces the inert PURASPEC 2272 – Cl-guarding support media
at the
bottomcan
of have
the high
temperPURASPEC
2272 is plant
a patented solution which
llustrates thesupport
impactmedia
a wetting
incident
on LTS
performance.
An ammonia
ature shift (HTS) reactor, (Figure 14), and cap- provides protection by helping to stop chlorides
e product strategy, including a Cl-guard layer (5% bed depth) over the main bed catalyst.
tures chloride which would otherwise poison the from reaching the LTS catalyst. Chlorides are
wo years on-line
the performance
was catalyst
good with
low CO slip very
(<0.2%)
andand
thesoreaction
low temperature
shift (LTS)
downstream.
soluble
are mobile when wetted. This
d little signs of poisoning.
means that condensation on a LTS catalyst can
Development of PURASPEC 2272 absorbent
distribute chlorides throughout the bed and have
JM has used its expertise in purification science a severe impact on catalyst performance.
ng a plant trip
which resulted in the LTS being wetted, the CO slip increased to End of Run
along with its proven STREAMLINE engineering
s. Consequently,
reactionPURASPEC
exotherm moved
deeper into
the bed
less
skills the
to develop
2272 –much
an innovaWetting
risk - becoming
Dewpoint consideration
Performancetive
Indicators
(KPI)
over
this
incident
are
shown
in
Figure
13.
new product which combines the functions of To achieve the lowest CO slip LTS catalysts are
a low pressure drop support with that of a chlo- run close to dewpoint. Hence as shown figure
ride trap.
15, dewpoint at the top of the LTS traditional
The development
of PURASPEC
2272
was & location
for a4 dedicated
Cl-guard above catalyst
Nitrogen + Syngas
2019 International
Conference
Exhibition (Berlin
- 7 March 2019)
made in JM’s research facilities in Billingham, (B) is typically below <25ºC. The location for
UK where the effectiveness of the alkali promoted PURASPEC 2272, at the bottom of the HTS vesabsorbent was tested using with reactor tempera- sel (A), gives a much greater safety margin.
Improvements to Water Gas Shift Process
ture 430ºC, pressure: 30 bar and steam: dry gas
The use of PURASPEC 2272 at a location below
ratio: 0.5 short term 25 day high GHSV test was the HTS gives several benefits:
Figure 13 KPI showing
performance
of performance
an LTS system
a wetting
incident
Figure 13:
KPI showing
of before/after
an LTS system
before/after
a wetting incident
After
the wetting damage the inefficient LTS performance significantly increasedwww.digitalrefining.com/article/1002381
production costs. The plant
8 November 2019
therefore made an unplanned shutdown to change the LTS catalyst. An estimate of the production costs for
this event was in the range $1,000,000 – $5,000,000.
PURASPEC 2272 – Cl-guarding support media
• dewpoint margin is above
200ºC
Figure 14: Location for installation of PURASPEC 2272 at HTS exit
• chlorides are kept out of
LTS reactor
PURASPEC
• should wetting occur,
chlo- 2272 is a patented solution which provides protection by helping to stop chlorides from reac
the LTS
catalyst. Chlorides are very soluble and so are mobile when wetted. This means that condensa
rides can leave from
a drain
on
a
LTS
catalyst can distribute chlorides throughout the bed and have a severe impact on cata
rather than enter LTS
performance.
The first reference for the
technology is a 1360 MTPD
Kellogg ammonia Wetting
plant, operrisk - Dewpoint consideration
ating at 120% of design capacity with parallel design HTS
Toeach
achieve
the lowest CO slip LTS catalysts are run close to dewpoint. Hence as shown figure 15, dewp
and LTS vessels in
vesat
the
top
of
sel the catalyst was supportedthe LTS traditional location for a dedicated Cl-guard above catalyst (B) is typically below <2
via a conventional
Thearrangelocation for PURASPEC 2272, at the bottom of the HTS vessel (A), gives a much greater safety mar
ment of ceramic balls above a
Figure 14: Location for installation of PURASPEC 2272 at HTS exit
semi-elliptical outlet collector, Figure 14 Location for installation of PURASPEC 2272 at HTS exit
Figure 16
JM were able
to analyse the
PURASPEC
2272 is a patented solution which provides protection by helping to stop chlorides from r
pressure dropthe
profile
LTS through
catalyst. Chlorides are very soluble and so are mobile when wetted. This means that conde
the catalyst bed and support
on a LTS catalyst can distribute chlorides throughout the bed and have a severe impact on
media using their proprietary
performance.
STREAMLINE software, JM
were able to analyse the flow
regime through
the risk
catalyst
Wetting
- Dewpoint consideration
support balls, Figure 17.
From this analysis the following improvements
To achieve were
the lowest CO slip Improvements
LTS catalyststoare
run close
to dewpoint.
Water
Gas Shift
Process Hence as shown figure 15, d
developed for at
both
the the
top HTS
of the/LTS traditional location for a dedicated Cl-guard above catalyst (B) is typically below
LTS reactors, Figure 18.
The location
for PURASPEC
2272,
at the bottom of the HTS vessel (A), gives a much greater safety
• dewpoint
margin is above
200ºC
• HTS
• chlorides are kept out of LTS reactor
o DYPOR as SHIFTSHIELD
o KATALCO 71-5F
as thewetting occur, chlorides can leave from a drain rather than enter LTS
• should
catalyst bed
o PURASPEC 2272 support
first reference for the technology is a 1360 MTPD Kellogg ammonia plant, operating at 120% of design
as Cl absorbingThe
STREAMLINE
capacity
with parallel
design
HTSFigure
and
LTS
vessels
ina Cl-guard
eachsection
vessel
thesection
catalyst was supported via a
Locations
in the shift
media.
Figure
15 Locations
for 15:
a Cl-guard
inforthe
shift
conventional
arrangement
of
ceramic
balls
above
a
semi-elliptical
outlet
collector,
Figure 16
• LTS
o KATALCO 83-3
as ofthe
The use
PURASPEC 2272 at a location below the HTS gives several benefits:
catalyst bed
o DYPOR
support
as
12
Nitrogen + Syngas 2019 International Conference & Exhibition (Berlin 4 - 7 March
STREAMLINE system.
HTS LTS
The anticipated improvement
in LTS performance and
life extension from using
PURASPEC 2272 is shown in
figure 19, based on steady state
operation.
In addition to this life extension by keeping some Cl safely
16 – Arrangement
of HTS/LTS
andcollector
outlet collector
Figure 16 Figure
Arrangement
of HTS/LTS
and outlet
Figuredrop
15: Locations
for a Cl-guard
in the bed
shift and
section
JM were able to analyse the pressure
profile through
the catalyst
support media using their
proprietary
STREAMLINE
software,
JM
were
able
to
analyse
the
flow
regime
through
the catalyst
www.digitalrefining.com/article/1002381
November
2019 9 support
balls, Figure 17.
The use of PURASPEC 2272 at a location below the HTS gives several benefits:
figure and
19, based
on steady
state operation.
se the pressure drop profile through the catalystinbed
support
media
using their
NE software, JM were able to analyse the flow regime through the catalyst support
Figure 18 – Case study – improvements to HTS/LTS loadings
The anticipated improvement in LTS performance and life extension from using PURASPEC 2272 is shown
in figure 19, based on steady state operation.
e 17 – STREAMLINE
analysis
of pressure
drop of
gradient
at HTS outlet collector
Figure 17
STREAMLINE
analysis
pressure
drop gradient at HTS outlet collector
Figure 19 Expected performance of LTS with PURASPEC 2272
Figure 19 – Expected
following improvements
werethe
developed
for both
HTS
/ LTS reactors,
Figureperformance
18. of LTS with PURASPEC 2272
guarded outside
LTS reactor
then the
in the
event
of unexpected transient conditions in which conJM’s LTS technology for self-guarding catalysts
In addition to this life extension by keeping some Cl safely guarded outside the LTS reactor then in the event
densation may occur at the top of theofLTS
bed
the
has
continued to evolve so catalysts offer ever
unexpected transient conditions in which condensation may occur at the top of the LTS bed the use of
R as SHIFTSHIELD
use of PURASPEC 2272 provides significant
longer
livesprotection
with reliable
performance,
JM’sdamaging
cata- event.
PURASPEC pro2272 provides
significant
against what
would be a potentially
LCO 71-5F tection
as the catalyst
against bed
what would be a potentially dam- lyst science and manufacturing processes are key.
event.
The LTS duty is vulnerable to being easily
SPEC 2272aging
support
as Cl absorbing STREAMLINE media.
Applications of the PURASPEC 2272 are damaged by wetting and chlorides. JM’s cataincreasing quickly since launch in Nitrogen
lyst technology
leadsquickly
in terms
of surviving
wetApplications ofand
the PURASPEC
2272 are increasing
since launch
in Nitrogen and
Syngas Berlin in
March 2019, the
following references are already now in-service, with these customers benefiting from
Syngas Berlin
in– Expected
Marchperformance
2019, ofthe
Figure 19
LTS following
with PURASPECref2272 ting incidents due to product strength. The new Cl
increased chloride protection for the downstream LTS.
erences are already now in-service,
with these guard PURASPEC 2272 adds a further new layer
ALCO
83-3
as
the
catalyst
bed
benefiting
from
increased
chloride
of protection
to the LTS catalyst from chloride that
In addition tocustomers
this life extension
by keeping some
Cl safely
guarded outside
the LTS reactor
then in the event
Process
Capacity,
mtpd inadvertent
Region
of unexpected
transient conditions
which condensation
may occur at the
top of the
LTS
bed theause
of if wetting
for theinsystem.
downstream
LTS.
can
impact
bed
occurs.
R support
asprotection
STREAMLINE
PURASPEC 2272 provides significant protection against what would be a Ammonia
potentially damaging event. 1,600
Conclusion
FSU
KATALCO, PURASPEC and STREAMLINE are trademarks of the
Ammonia Johnson Matthey600
Europe
group of companies.
Over many decades water gas shift technologies
14
Nitrogen + Syngas 2019 International Conference & Exhibition (Berlin 4 - 7 March 2019)
for both HTS and LTS have been improved,
with References
1 and
Patent
GB 2543955
Applications the
of theuse
PURASPEC
2272
are
increasing
quickly
since
launch
in
Nitrogen
Syngas
Berlin
in – Water-Gas Shift Process, Publication Date
of shape for pressure drop reduction in
24.01.2018
March 2019,the
the HTS
following
references
are
already
now
in-service,
with
these
customers
benefiting
from
recent JM technology innovation.
increased chloride protection for the downstream LTS.
2 The Importance of Catalyst Design in Managing the Impact of
Transient Operating Conditions in Ammonia Plants, 2014 AIChE
tional Conference & Exhibition (Berlin, 4 - 7 March 2019)
13 Safety Symposium, Farnell P W;
Ammonia
Process
Capacity, mtpd
Region
Carlsson M
Ammonia
1,600
FSU
3 Experience with Guards for Low Temperature
Improvements to Water Gas Shift Process
Shift Catalyst and Extended Life; 1978 AIChE
Ammonia
600
Europe
Ammonia Safety Symposium, Lundberg W. C.;
Ammonia
1,400
FSU
4 Low Temperature Shift Catalyst Developments
14
Nitrogen + Syngas 2019 International Conference & Exhibition (Berlin 4 - 7 March 2019)
Ammonia
1,200
Europe
& Related Process Effects; British Sulphur
Nitrogen 1988, 5 5. Kitchen D
Table
3:
PURASPEC
2272
references
as
Oct
-2019
Table 3 PURASPEC 2272 references
as Oct -2019
John Brightling
The Use and Abuse of Low Temperature
Shift Catalyst; 1989 AIChE Ammonia Safety
Symposium, Kitchen D., Henson W.G.S.,
HTS
LTS
Conclusion
Madsen J.K.;
Over many decades water gas shift technologies for both HTS and LTS have been improved, with the use
LINKS
of shape for pressure drop reduction in the HTS recent JM technology innovation.
More articles from: Johnson Matthey
JM’s LTS technology for self-guarding catalysts has continued to evolve so catalysts offer ever longer lives
More articles from the following
with reliable performance, JM’s catalyst science and manufacturing processes are key.
categories:
Catalysts and Additives
The LTS duty is vulnerable to being easily damaged by wetting and chlorides. JM’s catalyst technology leads
Heat Transfer
in terms of surviving wetting
incidents
duestudy
to product
strength.toThe
new Clloadings
guard PURASPEC 2272 adds a
Figure
18 – Case
– improvements
HTS/LTS
Figure 18 Case study – improvements to HTS/LTS loadings
further new layer of protection to the LTS catalyst from chloride that can impact a bed if wetting inadvertent
occurs.
The anticipated improvement in LTS performance and life extension from using PURASPEC 2272 is shown
n figure 19, based on steady state operation.
KATALCO,
8 PURASPEC
November 2019and STREAMLINE are trademarks of the Johnson Matthey group of companies.
References:
www.digitalrefining.com/article/1002381