A
B
CO compression- dehydration
CO compression- dehydration
CO to sequestration
CO to sequestration
Feed puri cation
Feed puri cation
CO (Post-Comb)
Nat. gas
Nat. gas
CO
CO
Ammonia compressor
Ammonia compressor
Steam
(Pre-combustion)
(Pre-combustion)
Steam
CO removal
Fired heater
CO removal
2-stg. PSA pkg.
CO shift
Syngas compression
Ammonia synthesis
Pre- reformer
CO shift
Syngas compression
Ammonia synthesis
2-stg. PSA pkg.
ATR
CR
ATR
GO2
GO2
GN2
GN2
ASU
ASU
Ammonia
Ammonia
Figure 3A Case 5: ATR with PSA + , H2RFire, and pre-combustion capture 3B Case 6: ATR with CR, PSA + , H2RFire, and pre-combustion capture
A
B
CO compression- dehydration
CO compression- dehydration
CO to sequestration
CO to sequestration
Feed puri cation
Feed puri cation
CO (Post-Comb)
CO (Post-Comb)
Nat. gas
Nat. gas
CO
CO
Ammonia compressor
Ammonia compressor
(Pre-combustion)
(Pre-combustion)
HRC
HRC
CO removal
CO removal
2-stg. PSA pkg.
Syngas compression
Ammonia synthesis
Syngas compression
Ammonia synthesis
CO shift
CO shift
POx
POx
NWU
GO2
GO2
GN2
GN2
ASU
ASU
Ammonia
Ammonia
Figure 4A Case 7: POx with PSA + and pre-combustion capture 4B Case 8: POx with nitrogen wash and pre-combustion capture
recovery comparable to nitrogen wash (see Figure 3A ). Fired heaters use hydrogen-rich fuel to minimise combustion-related CO₂ emissions. Higher hydrogen production requirements increase front-end capacity, creating a trade- off between carbon intensity and capital investment. Case 6: ATR with convective reforming, two-stage PSA, hydrogen-rich firing, and pre-combustion capture This case adds a CR in series with the ATR and operates at a higher steam-to-carbon ratio (see Figure 3B ). High-temperature heat recovery provides additional reforming duty, reducing natural gas and oxygen requirements but also reducing high-pressure steam generation. The configuration illustrates the close interaction between reforming efficiency, steam balance, electrical power demand, and carbon intensity. Case 7: POx with two-stage PSA and pre-combustion capture This configuration employs POx, operating at substantially higher temperatures than ATR and without a reforming catalyst (see Figure 4A ). Oxygen demand is somewhat higher, but
methane slip is significantly lower. Integrated heat recovery supplies process heating and steam superheating, minimising the requirement for conventional direct-fired process heaters and associated emissions.
Case 8: POx with nitrogen wash and pre-combustion capture
This case is similar to Case 7 but uses a NWU for hydrogen purification (see Figure 4B ). No nitrogen-wash recycle is applied. Despite the absence of recycle, the configuration achieves approximately 97% CO₂ capture because the high-temperature POx operation results in very low methane slip. Steam system The high-pressure steam level and degree of superheat were optimised for each configuration to minimise fired heater duty and reduce overall CI. Steam turbine drives were employed for major compression equipment (syngas and ammonia compressors) when sufficient high- quality steam was available; otherwise, motor drives were used to maintain energy efficiency. Surplus superheated high-pressure steam was expanded through back-pressure or condensing
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