A
B
Post- combustion capture (~95%)
CO compression- dehydration
CO compression- dehydration
CO to sequestration
CO to sequestration
CO (Post-Comb)
Feed puri cation
Feed puri cation
Feed
Feed
Ammonia compressor
Ammonia compressor
CO (Post-Comb)
CO
CO
(Pre-combustion)
(Pre-combustion)
CO removal
CO removal
Steam
Steam
Air
Air
Primary reformer
Secondary reformer
HT & LT shift
Methanation & dryers
Syngas compression
Ammonia synthesis
Primary reformer
Secondary reformer
HT & LT shift
Methanation & dryers
Syngas compression
Ammonia synthesis
Rich H
Rich H
Loop purge
Loop purge
Waste gas to fuel
Waste gas to fuel
HRU
HRU
Ammonia
Ammonia
Figure 1A Case 1: SMR with SR and pre-combustion capture 1B Case 2: SMR with SR and PoPCCS
CO (Post-Comb)
CO (Post-Comb)
A
B
CO compression- dehydration
CO compression- dehydration
CO to sequestration
CO to sequestration
Feed puri cation
Feed puri cation
Nat. gas
Nat. gas
HPS superheating
HPS superheating
CO
CO
Ammonia compressor
Ammonia compressor
(Pre-combustion)
(Pre-combustion)
Steam
Steam
Fired heater
Fired heater
CO removal
CO removal
Pre- reformer
CO shift
Pre- reformer
CO shift
N wash
Syngas compression
Ammonia synthesis
Syngas compression
Ammonia synthesis
NWU
ATR
ATR
GO2
GO2
GN2
GN2
LN2
LN2
ASU
ASU
Ammonia
Ammonia
Figure 2A Case 3: ATR with nitrogen wash and pre-combustion capture 2B Case 4: ATR with nitrogen wash recycle, H2RFire, and pre-combustion capture
Case description Each configuration is briefly described below to highlight the principal process steps, integration features, and carbon management approach. The eight cases are illustrated in Figures 1 to 4 . Case 1: SMR with SR and pre-combustion capture This base case represents a conventional modern ammonia configuration using SMR followed by SR (see Figure 1A ). CO₂ removed from the process gas is compressed and dehydrated for sequestration. The configuration provides moderate decarbonisation using well-established technology with extensive commercial operating experience. Case 2: SMR with SR and combined pre- and post-combustion capture This case extends Case 1 by capturing CO₂ from the reformer flue gas and combining it with the pre-combustion CO₂ stream for compression, dehydration, and sequestration (see Figure 1B) . Post-combustion capture reduces residual reformer-stack emissions while retaining the conventional SMR/SR process architecture.
Case 3: ATR with nitrogen wash and pre-combustion capture
This configuration employs ATR at the lowest commercially viable steam-to-carbon ratio (see Figure 2A ). An integrated air-separation unit (ASU) supplies oxygen and process nitrogen, while a NWU purifies hydrogen. Separate fired heaters provide process preheating and high- pressure steam superheating using natural gas blended with plant off-gas as fuel. Case 4: ATR with nitrogen wash recycle, hydrogen-rich firing, and pre-combustion capture This case extends Case 3 by recycling carbon- containing streams to the ATR and using internally generated hydrogen-rich fuel for fired heaters (see Figure 2B ). Recycling increases front-end equipment size and oxygen demand, but substantially reduces direct carbon emissions by retaining carbon within the process for pre-combustion capture. Case 5: ATR with two-stage PSA, hydrogen- rich firing, and pre-combustion capture This configuration replaces the NWU with a PSA + system designed to achieve hydrogen
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