Installation of S-50 for Ammonia Plant Energy Savings

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Installation of S-50 in Ammonia Plants
Method · June 2021
DOI: 10.13140/RG.2.2.33710.64327
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Installation of S-50 in Ammonia Plants
By
Prem Baboo
DGM (Production & Process)
Abstract
Installation of S-50 ammonia synthesis converter
along with waste heat boiler in downstream of
existing S-200 ammonia synthesis converter is
one of the major schemes of Energy Saving
Project of Ammonia plant. The energy saving
reported 0.18 G.Cal/T of Ammonia. Several
ammonia plants have installed an additional
ammonia synthesis converter in combination
with a HP steam waste heat boiler, downstream
of the existing ammonia converter. The result is
increased conversion per pass, reduced
compression requirements due to the smaller
recycle gas stream, and improved waste heat
recovery. Among the methodologies aimed at
finding energy saving opportunities, pinch
analysis linked to power and steam modeling has
proved to be a powerful way for determining
projects to improve the overall energy efficiency
of industrial sites. This procedure has been
applied successfully in many industrial facilities,
allowing optimal energy recovery in the process
and hence reduction of fuel consumption.
Keywords
Converter, S-50, Ammonia, Energy, waste heat
boiler.Revamp.
Introduction
The Topsoe S-250 system uses two radial flow
converters placed in series with waste heat
boilers between the converters and after the last
converter (see Figure). This system compared to
the S-200 series (employing one converter) is
claimed to increase the conversion per pass and
reduce the energy use. Similar energy savings
and increase in the conversion per pass can also
be achieved with the replacement of the S-200
With a three-bed radial flow converter with two
internal heat exchangers. To enable the HP
steam production, Topsoe has recognized the
following modifications in the existing ammonia
synthesis converter configurations. According to
Topsoe, The introduction of S-50 converter
along with S-200 converter in the existing plants
as shown in the figure-2. The purified synthesis
gas contains a small amount of impurities,
mainly the inert Ar and CH4. To avoid an up
concentration of inert, continuous purge from
the synthesis loop would be required. The
ammonia synthesis loop has been designed for a
maximum pressure of 245 kg/cm2g. The normal
operating pressure will be 200 kg/ cm2g.
depending on load and catalyst activity. The
normal operating temperatures will be in the
range of 360 to 525 °C for the 1st bed and 370 to
460°C for the 2nd bed. The heat liberated by the
reaction is utilized for high pressure steam
production in the loop waste heat boiler, E 3501
and preheat of high pressure boiler feed water.
The make-up synthesis gas flow, which is in the
range of 176693 Nm2h, leaves the make-up
synthesis compressor group at 200 kg/cm2g and
39°C.The make-up synthesis gas is further
cooled in the make-up gas chiller, E 3514,
giving an outlet temperature of about 22°C.
The mixing of make-up synthesis gas and
circulating synthesis gas takes place between the

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first ammonia chiller, E 3506, and the second
ammonia chiller, E 3507 The addition decreases
the temperature of the mixture to about 18°C,
due to part evaporation of the ammonia already
condensed. The final condensing takes place in
the second ammonia chiller, where the gas/liquid
mixture is cooled to about 12°C . The
gas/liquid mixture is separated in the ammonia
separator, B 3501. and during normal operation
about 645915 Nm2/h of synthesis gas leaves the
top as recalculating gas and about 83272 Nm2/h
(62377 kg/h) of liquid ammonia leaves the
bottom. The approximate converter inlet gas
composition is shown below.
Hydrogen: 64.2 mole %
Nitrogen: 21.4 mole %
Ammonia: 5.6 mole %
Methane: 5.9 mole %
Argon: 2.9 mole %
100.0 mole % (mole weight: 10.29)
The main inlet flow to the converter, R 3501, is
introduced through two inlet nozzles at the
bottom. The inlet gas passes up through the
annular space between the pressure shell and the
insulated basket, and thereby the pressure shell
is kept relatively cool.The temperature profile of
the shell may be followed by the eleven
thermocouples mounted on the shell to ensure
that the design temperature of the pressure shell
(370°C) is never exceeded.The approximate
composition of the converted gas is
Hydrogen: 51.8 mole %
Nitrogen: 17.2 mole %
Ammonia: 21.0 mole %
Methane: 6.7 mole %
Argon: 3.3 mole %
Cooling of Converter Effluent Gas:
The converter effluent gas is cooled in six steps
before purge gas removal, make-up synthesis
gas addition and final condensing of ammonia.
The purpose of the cooling taking place in the
first five heat exchangers, is
1. to recover waste heat for HP
steam production and BFW
preheat
2. to preheat the converter inlet gas
and
3. to save refrigeration energy in
the ammonia chillers.
4. The converter effluent gas
passes the tube side of the six
heat exchangers and the
anticipated cooling temperatures
are shown as:
Heat Exchanger Temperature °C
E 3501 Loop Waste Heat Boiler 456/350 °C
E 3502 BFW Pre heater 350/269 °C
E 3503 Hot Heat Exchanger 269/61 °C
E 3504 Water Cooler 61/38 °C
E 3505 Cold Heat Exchanger 38/28 °C
E 3506 First Ammonia Chiller 28/23 °C

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Fig-1

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June 2021
6
Fig-5
Detail Installation of S-50
Fig-6 Fig-7
Operating conditions
Inlet Gas
Temperature o
C 366
Pressure Kg/cm2
177
Total flow Nm3
/hr 550,656
Composition
H2 Vol% 52.72
N2 Vol% 17.57
Inerts, CH4 + Vol% 9.69
NH3 Vol% 20.02
Outlet Gas
Temperature o
C 419
Pressure Kg/cm2
176
Total flow Nm3
/hr 531,482
Composition
H2 Vol% 49.21
N2 Vol% 16.40
Inerts, CH4 + Vol% 10.04

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NH3 Vol% 24.35
Table- 1 Fig-8
Fig-9
Catalyst
Type KM1
Size mm 1.5-3
Diameters, OD (effective)/ ID mm 2,896 / 760
Height (excl./incl. bottom cone part) m 20,100 / 21,200
Volume m3
125,4
Table-2
Mechanical Data (Pressure Vessel)
Type Vessel with top manhole
Inner diameter mm 3,000
Inner length (T-T) mm 20,250
Normal operating pressure Kg/cm2
g 177
Design pressure Kg/cm2
g 245
Hydrogen partial pressure, design Kg/cm2
130
Temperature of Operating Design
Cover and cylinder part o
C 366 430
Spherical bottom o
C 366 430
Bottom forging o
C 419 450
Bottom flange o
C 419 450
Nozzle sizes
Main inlet inch 16
outlet inch 16
Table-3

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Installation of S-50 ammonia synthesis converter
along with waste heat boiler in downstream of
existing S-200 ammonia synthesis converter is
one of the major scheme of Energy Saving
Project of Ammonia plant.
Parameters
units
Line-II Line-I
Design Design
Line-I Line-II
Conveter inlet flow Nm³/h 658400 766490 656158 645915
Make up gas flow Nm³/h 184520 185800 179904 182780
HG from PGR Nm³/h 0 7160 0 0
Converter Feed comp.
H2 vol% 0.6419 0.6258 0.6415 0.6424
N2 vol% 0.1974 0.2185 0.2132 0.2141
NH3 vol% 0.0450 0.0450 0.0578 0.0559
Ar vol% 0.0327 0.0303 0.0287 0.0291
CH4 vol% 0.0830 0.0804 0.0588 0.0584
Converter outlet
comp. 1.00 1.00 1.00 1.00
H2 vol% 0.5195 0.5118 0.5184 0.5173
N2 vol% 0.1575 0.1706 0.1721 0.1724
NH3 vol% 0.1860 0.1870 0.2094 0.2100
Ar vol% 0.0385 0.0358 0.0329 0.0333
CH4 vol% 0.0985 0.0949 0.0672 0.0670
1.00 1.00 1.00 1.00
Conerter inlet pressure kg/cm²g 179.80 195.40 220.00 220.00
Conerter outlet pressure kg/cm²g 178.00 193.40 216.00 216.00
Pressure Drop kg/cm²g 2.00 2.00 4.00 2.00
Ist Bed Temperature
Inlet °C 364.00 363.50
Outlet °C 491.00 498.50
IInd Bed Temperature
Inlet °C 355.00 387.60
Outlet °C 435.00 436.70 457.00 456.00
Table-4
Pre shutdown activity

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Fig-10
After completion of steel cage of top portion of
civil foundation of S-50 ammonia synthesis
converter, anchor bolts were position with the
help of template and clearance given for further
civil job. Shrinkom-20 were used for pockets
grouting after removal of template.
Skirt were placed on foundation and leveled at
elevation of 106.200 mtr. with the help of MS
plats on 27.07.2011and gaps between base plate
of skirt and civil foundation were filled by
Shrinkom-20.
Fig-11
S-50 ammonia synthesis converter were placed
and leveled / centered on skirt with the help of
Demag CC2800-1and CC2000 crane on
05.08.2011. Erection plan submitted by M/s
Sarens Heavy Lift India Pvt. Ltd., party engaged
by piping & equipment erection contractor (M/s
Satnam Global Infra projects Ltd., Delhi) for
heavy equipment erection along with cranes is
enclosed. After opening of top cover and outer
screen panel covers, joint inspection was done
by NFL / HTAS to check any damage during
transportation / erection and found Ok. Lot of
rust as scale was found on inside surface of
reactor which was vacuum cleaned before
catalyst loading.

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Fig-12
After inspection, catalyst was charged with the
help of shower head from 27.01.2012 to
30.01.2012 and balance from 08.02.2012 to
12.02.2012. The approximate density of
catalyst achieved was 2.93 Kg/litre. During
charging of catalyst, support provided for centre
screen and outer screen panels were removed
which was provided by the supplier to avoid any
damage while transit.
After catalyst loading, outer screen panel cover
boxed up and tack weld as instructed by HTAS.
Gland packing of stuffing box (centre screen and
outer screen panel cover flange) checked and
found OK. Top cover and bottom cover were
boxed up with the help of bolt tightening device
and lip seal welded with Inconel filler wire.
Insulation job of S-50 Ammonia synthesis
converter (160.0 mm thick) and connecting pipe
line job done by M/s Kaefer Punj Lloyd Limited.
S-50 Loop a philosophy
• Higher conversion 35.5 % as compared
to 28.3% in S-200
• Ammonia concentration at the outlet of
S-50 = 24.35% as compare to 20.02% in
S-200
• Lower circulation rate as compared to S-
200 for same load
• Higher steam generation 82 T/hr as
compared to 70 T/hr in S-200
Shutdown Activities
All the prefabricated pipelines were hydrotest at
367.5 Kg/cm2
before hookup with existing
header and S-50 converter. RT of the all weld
joint done on half weld and UT at full weld joint
of pipe line. Stress reliving of alloy steel pipe
weld joint (2.25Cr 1Mo steel) was done as per
ASME section and Hardness was achieved
below 220 HB. Instrumentation, Electrical and
Structure job were taken care by respective
department.
Ammonia Synthesis shut down pre-
conditions
Front end load has been reduced to 60% of the
normal capacity. Loop pressure is reduced to
130 to 150 g/cm2
. Recycle gas lined up from line
I. Cut off purge gas to reformer fuel. 35TV4
taken on manual and its position is fixed at
desired level to control the converter bed
temperature.343HV609 closed & anti surge
valve 343HV615 opened. Reduce the BFW flow
to E3502 by adjusting 32HV32 . Stop make up
to loop . Close compressor suction valve,
343HV601. Check that venting is shifted to
33PV62.Stop the purge gas flow by closing

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35FIC31 . Close 35LIC22 & block level in B3501. Block the ammonia chillers
level & B3510 level. Refrigeration compressor
is to be kept running. Watch the converter shell
temp. (Design temp. = 370 0
C).If it increases,
open the converter inlet valve 35HV1 full
&close the cold shot 35TV4.Prepare for start up
of synthesis section after rectifying tripping
cause.
Shut Down for Installation S-50
At loop pressure around 130 to 150 kg/cm2
,
interrupt make up gas flow to the loop. Catalyst
cooling is started by increasing the circulation
flow. Cooling rate to be maintained to 50 0
C/hr
maximum. When the catalyst is cooled down to
50 0
C, the compressor is shut down. check that
inlet & outlet valves closed in field. During
cooling down, the BFW pre heater, E3502 &
loop boiler, E3501 are isolated. Depressurize
loop to 60 kg/cm2. Drain B3501 completely,
Drain the liquid inventory in ammonia chillers &
accumulators in B3510 & send it to storage via.
B3503.Stop refrigeration compressor. The BFW
pre heater, E3502 & loop boiler, E3501 are
depressurized before the loop depressurization.
Depressurize loop through 35FV31. Reduce the
loop pressure to 1 to 3 kg/cm2
Methanation Section
Normal Shut Down
Reduce the heat input to R3311 by slowly
closing 33TRC60. Cool the catalyst @ 80
0
C/Hr. by process gas. When all the temp are
around 150 0
C, the process gas flow to R3311 is
stopped by activating IS6 thus closing
33USV161. Purge the reactor with nitrogen &
keep it under nitrogen pressure. In normal case
purge & keep the methanator under nitrogen
pressure in hot condition.
GV Section Normal Shut down
It includes three main steps:
1. Plant capacity reduction to 40%.
2. Effective shutdown of plant.
3. Depressurizing, draining & Purging
Pre-Conditions
LT Shift section & Methanation section
shutdown has already been taken.PG venting has
been shifted to 33PV60.Surplus gas to reformer
fuel is cut off. Reduce the GV solution
circulation rate to 80% of the design capacity.
Decrease the flow of PG to F3303 by partly
opening 33HV25.Close 33HC21 there-by
shifting the venting on 33PV61 &33HV25. Keep
F3303 under pressure at 15 - 20 kg/cm2
by
putting that set point on 33PV60.If pressure
could not be maintained open NG to absorber.
If 33LRC4 level shows a rising trend, then
transfer some of the level to T3301 through
P3304. As the CO2 flow through F3302 has
decreased considerably, stop CO2 blower &
F3302 pressure is controlled on 33PV24. Inject
nitrogen, if required. Regenerate the solution
for at least 4 hours or till the F/C of the solution
comes below 0.17.with process gas heat through
E3302A/B. Maintain venting at 33HV25 as per
the heat requirement in E3302A/B.
Depressurize F3301 progressively on 33PV33 &
33PV29.Close 33HV25, there taking total
venting on 33PV61. Complete the regeneration
through the heat input from E3302A/B. Stop
the motive steam to ejector X3301 and overhead
condensate feed to E3303.Open the local vent.
Increase the temp. of lean solution on 33TIC24 .
Transfer solution from F3301 to T3301 through
the pump P3304.Stop the aeration & GV
filtration unit .Drain all the solution lines &
towers to T3301Isolate, drain, purge & wash the
solution pumps .Depressurize F3303, purge with
nitrogen. Also purge the solution line to F3301
top. Depressurize; purge the towers F3301 &
F3302 with nitrogen .Maintain GV solution
temp. in T3301 at 50-60 0
C.
Start the GV solution in close loop
T3301P3305 A3301 A3302 A3303 
T3301

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GV Section Start up procedure conditions Startup after long S/D, in which major welding
job done in the reboiler & GV towers
.
Isolate F3303 (close 33HC21), close I/V at
methanator I/L, Close 33LIC20 & it’s
I/V.33HV25 kept opened. All solution line
drains, tower drains, level gauge’s drains,
sample connection drain’s closed. F3303,
F3302, F3301 purged with nitrogen. Analyze for
oxygen contents, it should be below 0.1%.
Plant Passivation
Plant passivation is done for provide the
protective layer of OF V2O5 on the metal
surface.
Static Passivation
It is done for passivation in Re boilers.
Prepare 23.5% K2CO3 & 0.4% V2O5 solution .
F3301 bottom is filled up with solution so that
E3302A/B, with solution inlet & steam outlet
pipes are completely filled, up to the reboiler
take off trey to allow solution to flow by gravity,
by means of P3305 feeding solution from
T3301. Pressurize F3301 with nitrogen to 1.7
kg/cm2
g . Start solution heating with quench
MP steam injection to E3302A/B (Temp. is
maintained at 130-140 0
C) .Start solution heating
with quench MP steam injection to E3302A/B
(Temp. is maintained at 130-140 0
C) . Analyze
the solution for K2CO3 & V2O5 every 8 hours.
Add V2O5, if it falls below 0.3% w/w.. Normally
solution concentration should remain constant.
Dynamic Passivation
Avoiding the presence of process gas &
pressurizing F3303 with recycle gas up to 15
kg/cm2
g.Pressurize F3301 & F3302 at 1.5
kg/cm2
g with nitrogen. Maintain solution flow
rates 33PIC22 = 1500 T/hr &33PIC23 = 275
T/hr. Adjust E3302 heating quench MP steam
pressure at 6 to 7 kg/cm2
and temp at 140 0
C so
that solution at F3301 & F3302 bottom should
not boiled off.. Maintain the heating rate of 10-
15 0
C.& F3301 & F3302 bottom temp. 110-115
0
C maximum. Continue this operation for next
72 hours , checking the column pressure,
solution concentration & temp. Analyze the
solution for K2CO3 & V2O5 every 8 hours. Add
V2O5, if it falls below 0.3% w/w.. Normally
solution concentration should remain constant.
At the end of the operation stop steam flow to
E3302A/B. When the solution cools down to
105 0
C, depressurize F3301 & F3302 to 0.05
kg/cm2
g.
Passivation after Long Shut down
Regenerated GV solution stored in T3301 is
used for this passivation. V2O5 concentration
should not be lower than 40% of total vanadium.
F3301 & F3302 are pressurized with N2 at 0.05
kg/cm2
g. Adjust E3302 heating quench MP
steam pressure at 6 to 7 kg/cm2
g and temp at 140
0
C so that F3301 & F3302 bottom temp. 105 0
C
maximum. Continue this operation for next 36
hours, checking the column pressure, solution
concentration & temp . Analyze the solution for
K2CO3 & V2O5 every 8 hours. Add V2O5, if it
falls below 0.3% w/w. Normally solution
concentration should remain constant.
Start up GV solution Circulation
Pressurize F3303 with natural gas up to 3
kg/cm2
. Start the pump MP3302B & start
filling F3301through with flow approx..150 to
175 T/hr. Start the pump MP3302B & start
filling F3301through with flow approx..150 to
175 T/hr. Put 33LIC9 in operation & stabilize
level in all the three towers. Put 33LIC7 in
operation. 33FIC23 flow may be increased to
200 to 225 T/hr. When normal level appears in
33LIC7, lined up MP3301C & start the pump.
Take 33FIC22 in operation at1200 T/hr. flow
rate. Stabilize the levels. Take 33FIC1 in
operation. Continue circulation, maintaining the
levels. Section is now ready for introduction of
process gas. Heating of circulation GV
solution with MP steam. Heat up the line by

June 2021
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opening 33HV116, maintaining pressure about
6-7 kg/cm2
. Lined up 33TIC5 maintaining
temp. of heating steam as per requirement
&introduce steam to E3302A/B. Put level
controller 33LIC21 in operation . Maintain
heating rate of 10 to15 0
C/hr. Maintain P3302
suction temp at 70 0
C by lining up of DM water
to E3306. Take E3307 & E3308 in operation.
Start the condensate pumps P3308 & P3321.Put
the level controllers 33LIC31, 33LIC34,
33LIC37 in operation. Start the condensate
pumps P3308 & P3321.Put the level controllers
33LIC31, 33LIC34, 33LIC37 in operation.
K3301 is kept isolated & 33PV26 is kept closed.
The overhead gases from F3302 venting through
33PV24 controlling on auto . Take level in
E3303 through 33LIC6.Keep the local vent open
at E3303 top. Check the temp. profile in the
towers .F3301 & F3302. When the bottom temps
of F3301& F3302 are stabilized, section is
ready.
Introduction of Process gas
Set 33PIC60 at a pressure 2 kg/cm2
less than PG
pressure at LT shift downstream.(about 20
kg/cm2
). Open bypass of 33HC21 & pressurize
F3303 to about 20 kg/cm2
.Open33HC21 full &
close 33HIC25 gradually, thus shifting venting
on 33PIC60 (Reset 33HC21 in IS1 & IS5.). In
parallel to above activity, line up ejector X3301.
Progressively stabilize the operation by
maintaining the tower pressures. Start K3301 &
adjust anti-surge valve. CO2 venting is now
totally shifted to 33PIC33-1, 2. Check that CO2
slip from F3303 is within range; adjust solution
flow to the towers.
Methanation Section Start up Procedure
Purge the methanator with nitrogen given
through permanent line. Insert blind in nitrogen
line. Open the methanator inlet I/V’s bypass
valve (U/S of 33USV161) & drain the
condensate from the line. Again close the
bypass. Open 33HIC164. 33HIC165 to be kept
close. Reset IS6, thus opening 33USV161.
Pressurize R3311 by slowly opening 33USV161
U/S I/V. at the rate of 1kg/cm2
/min. Heating is
started through 33HIC74. In case the catalyst
bed is having temp.,R3311 top vent 33HIC63 is
to be opened initially so that bed should not get
cooled .Maintain the heating @ 50 0
C/hr.
33TRC60 temp. can be increased either by
passing the process gas through E3209 &
controlling 33TV60-1 through 33HIC62 . Or by
putting 33TRC60 on auto. Keep 33TV60-2
close. Reaction will start at the temp. above
220-250 0
C. Continue heating up to 290 0
C at
33TRC60.Stabilize the temps in the bed.Analyze
the R3311 O/L sample for CO & CO2 contents,
when these contents come below 5 ppm. , shift
the venting at 33PIC62. The process gas is now
available for feeding in the synthesis
compressor.
Ammonia Synthesis Section start up
with use of Start up pre heater.
Take level in B3510 from storage tank. Transfer
level to E3506, E3514 & E3507 through level
controllers. Take level in B3503 through
35FIC30. Also fill the ammonia chillers to 60%
level. B3503 lined up to B3504 . Transfer level
to E3506, E3514 & E3507 through level
controllers. Take level in B3503 through
35FIC30. Also fill the ammonia chillers to 60%
level. B3503 lined up to B3504 . BFW level is
taken in E3501, vent valve opened & close
35FV1, 35HV3, 32HV32. Start synthesis
compressor with anti surge valves open &
discharge valves closed. Check that balancing
valve 343HV610 is opened. Start synthesis
compressor with anti surge valves open &
discharge valves closed. Check that balancing
valve 343HV610 is opened. Open 35HV1
&343HV614 by 10%. Check that circulation is
established across heater, indicated by 35PDI4.
Switch on the heater. Check for gas temp O/L
heater at 35TI41. Start to increase temp. of
circulating gas by increasing heater load . With
circulator anti surge valve full open, circulation

June 2021
14
is increased by opening 35HIC14. Increase the
bed temp. @ 30 to 50 0
C/hr. maximum.
Increase the bed temp. @ 30 to 50 0
C/hr.
maximum. When the reaction is started, slowly
decrease the heater load & cut off the heater. At
full circulation rate, maintain catalyst temp. by
putting 35TIC4 on auto. Maintain the loop
pressure by increasing the make gas flow @ 10
to 20 kg/cm2/hr. Normalize the boiler. Close
local vent, open the BFW feed valve & maintain
E3502 temp. by opening 32HV32. Start
refrigeration compressor**(If possible start it
before syn section s/u.). When normal level is
built up in B3501, liquid ammonia will start
flowing from B3501 to B3502 through 35LV22 .
The gas flashed off in B3502 is send to E3508 &
pressure is maintained at 25 kg/cm2
. The gas
flashed off in B3502 is send to E3508 &
pressure is maintained at 25 kg/cm2
. E3510
taken in operation. Inert gas flow can be
established on 35FIC40 through E3509.
Start up with out start up Heater
Keep 35TV3, 35TV4 & I/V at heater inlet close.
35LV22 lined up. Equalize loop & compressor
discharge pressure by opening bypass over
343FV607. Open 343HV608/ 609 of
recirculation. Open 35FV1 & 343HV 614 by
10%. Maintain the circulation in loop so as to
increase the bed inlet temp. Open 343HV614
slowly adjusting the circulation rate. Establish
BFW flow to E3502 & E3501. Steam generation
from E3501 will also start with start of ammonia
production .Increase loop pressure to normal by
increasing speed of compressor , closing the
anti-surge valve & increasing the make up
flow.Maintain the bed inlet temp. by 35TV3&4.
Parameters Affecting Performance
of the Loop
• Gas Composition
• Ammonia Concentration at Converter
Inlet
• Inert gas level
• H2 / N2 Ratio
• Reaction Temperature
• Circulation Rate
• Operating pressure
• Product removal
• Lower compressor power due to less
circulation
• Possible to achieve higher plant load
with same equipments
• Low loop pressure drop due to less flow
Advantages of addition of S-50
Loop
• Higher conversion 35.5 % as compared
to 28.3% in S-200
• Ammonia concentration at the outlet of
S-50 = 24.35% as compare to 20.02% in
S-200
• Lower circulation rate as compared to S-
200 for same load
• Higher steam generation 82 T/hr as
compared to 70 T/hr in S-200
• Lower compressor power due to less
circulation
• Possible to achieve higher plant load
with same equipments
• Low loop pressure drop due to less flow
Scheme Energy saving
Gcal/Mt (NH3)
Yearly Saving
(Rs.Crore /
year)
Investment
(Rs.Crores)
Payback Period
(Years)
Installation of S-50
converter and WHB
0.18 8.226 32.36 3.9
Table-5

June 2021
15
Conclusion
In order to arrive at the most attractive revamp
scheme it is of paramount importance that the
scheme is optimized based on the objective and
the specific conditions prevailing. The novel
revamp feature, the Haldor Topsøe ammonia
synthesis convertor S-50 is an attractive
alternative for increasing the capacity of the
reforming section in an ammonia plant.
References
1. How to Bring Existing Ammonia
Plants Up-to-Date by Svend Erik
Nielsen Haldor Topsøe A/S,
Lyngby, Denmark and Peter
Vang Christensen Haldor Topsøe
A/S, Lyngby,
Denmark.Ammonia technical
manual 2004
2. Dybkjær, I., “Advances in

Ammonia Con verter Design
and Catalyst Loading”,

pre sented at the NITROGEN
’97 Conference, Geneva,
Switzerland, Feb. 9-11, 1997
3. Nielsen S.E., Dybkjær I., ”Use of

Adia batic Prereforming in
Ammonia Plants”, Ammonia
Plant Safety & Related

Facili ties, Vol. 37, AIChE,
New York (1997)
4. Manual for reduction of
KM1Loaded in S-50 convertor
with upstream S-200 convertor
online by Haldor Topsoe.
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