modifications. In comparison, ATR and POx configurations in Cases 4 through 8 achieve higher direct carbon capture through pre- combustion removal and avoid the need for large-scale flue gas treatment. Their higher initial capital requirements must therefore be evaluated against carbon performance, utility demand, process integration, and project- specific operating objectives. Emerging low-carbon pathways Catalytic methane pyrolysis offers a potential route to very low-carbon ammonia by producing solid carbon rather than CO2, thereby avoiding conventional carbon capture and sequestration. Although the technology remains at pilot scale, integration of hydrogen produced by methane pyrolysis with ammonia synthesis could provide an alternative pathway where carbon sequestration infrastructure is limited. Catalytic methane pyrolysis converts methane into solid carbon and hydrogen without process-related CO2 formation. Each ton of ammonia would generate approximately 0.54 tons of solid carbon, which could potentially enter carbon black or other carbon markets if product quality permits. However, the size of existing carbon markets limits how much ammonia production could rely on such outlets. Economics therefore depend strongly on the value and disposition of the solid carbon. Broader deployment would require development of additional large-volume carbon applications. Other important challenges include catalyst life, reactor performance, solids handling, and reliable continuous operation at high temperature. Other emerging options include electrified reforming, which may complement ATR and POx configurations as access to low-carbon electricity expands. Conclusions Achieving deep decarbonisation in ammonia production requires technology choices that balance carbon performance, energy efficiency, operating reliability, and capital investment. Conventional SMR with combined pre- and post-combustion capture, represented by Case 2, provides the lowest capital
C apex & O pex indices
150
100
50
0
1
2
3
4
5
6
7
8
Case number
C apex index
O pex index
Figure 6 Capex and Opex indices of all cases
cost among the configurations evaluated. However, residual reformer flue gas emissions remain because of the assumed 95% post- combustion capture efficiency, while the large flue gas treatment system introduces additional equipment, utility demand, and operating complexity. ATR and POx configurations in Cases 4 through 8 achieve greater direct carbon capture by concentrating most carbon in the process gas for pre-combustion removal. These configurations avoid large-scale flue gas treatment and can achieve very low Scope 1 emissions. Their overall carbon intensity, however, also depends on oxygen demand, steam balance, electrical power consumption, and the carbon intensity of imported electricity. Technology selection therefore remains project-specific and should consider natural gas consumption, air separation requirements, steam and power integration, carbon sequestration infrastructure, capital cost, and operating requirements. Catalytic methane pyrolysis and electrified reforming remain emerging options requiring further commercial validation. For new ammonia projects targeting deep decarbonisation, ATR and POx with high levels of pre-combustion capture provide strong alternatives among the configurations evaluated. Final selection should be based on integrated carbon, energy, economic, and operating performance rather than capture percentage or initial capital cost alone.
VK Arora vka@kpieng.com
www.decarbonisationtechnology.com
33
Powered by FlippingBook