Low-carbon hydrogen is expected to have a large role in future energy systems. Recent research shows the short-term financial feasibility of blue hydrogen is often higher than green hydrogen. Ammonia production is particularly carbon-intensive due to its hydrogen production routes. This research focuses on the physics-based modelling of blue hydrogen production for ammonia synthesis, examining the influences of varying input conditions and economic scenarios on process performance and economics. Future energy systems will rely on flexible integrated solutions, emphasizing the importance of understanding how system parameters respond to diverse input conditions.

The ammonia plant consists of a desulphurization unit, a pre-reformer, an ATR, two water gas shift reactors, a physical absorption tower for CCS, a PSA for H2 purification and a Haber-Bosch ammonia synthesis reactor. Auxiliary components consist of heat exchangers, compressors and dehydration units. The modelling efforts focus on medium-fidelity models, reflecting the main thermodynamics and kinetics through first-order differentials assuming reactor simplifications. The plant simulations are based on plant operation in the Netherlands in 2030 under the following price assumptions: C_NH3= 0.472 €/kgNH3, C_elec= 41.77 €/MWh, C_NG= 22.64 €/MWh, C_CO2−tax= 0.135 €/kgCO2(eq), C_CCS= 0.05 €/kgCO2.

Each reactor model was separately validated through industrial data. Then the operational window was selected based on individual reactor limitations and the overall system chain performance: α=0.6, β=2.0, Tin=873.15K, Pin=2.8MPa. α and Tin are the most influential parameters from an economic and environmental perspective, showing the largest influence on levelized costs and emissions. Overall, under the simulated conditions, blue ammonia results in an 85% direct emission reduction compared to grey ammonia. The levelized costs of blue ammonia amount to 0.417€/kg and the NPV is 104 MEUR, the most influential economic parameters are the natural gas price and the ammonia selling price.

Three case studies were conducted in which specific economic and operational conditions were compared. Simulations of three IEA policy scenarios for 2030 show that the overall cost reduction in more sustainable scenarios is mainly driven by the lower natural gas price. Carbon taxes have a limited effect on the price of blue ammonia however do significantly increase the price of grey hydrogen compared to blue (a 0.11-0.17 €/kg difference). This results in a minimum 0.05 €/kgNH3 margin for the capture process costs in the stated scenario (0.09 €/kgCO2(eq) ), the other scenarios give a larger margin. Green ammonia gives a levelized cost of 0.457 €/kg NH3 under the same economic assumptions. The NPV is -480 MEUR, which is most affected by the electricity price and ammonia price. This research yields a 9% LCOA increase for green ammonia when compared to blue. The evolution of electricity prices is paramount in the financial competitiveness of green ammonia, more so than the CAPEX
evolution. The indirect emission intensity of green ammonia is lower than blue ammonia in the simulated conditions. However, this depends on the electricity source. Through carbon taxes blue and green ammonia can become cost-competitive to grey however this comes at a cost for the everyday consumer.
A simulation with dynamic operation yielded that inputting NG feed following seasonal natural gas pricing is not cost-effective when compared to steady-state production at the same seasonal pricing, even for +/-44% price fluctuations. The additional CAPEX costs for storage and larger process units are not sufficiently compensated by the lower variable OPEX costs. Further research should focus on
shorter-term supply and demand matching.

Overall, it can be concluded that this model can sufficiently simulate a blue hydrogen chain and be used for further simulation cases, also with alternative economic and operational assumptions. The technical parameters that affect blue ammonia production most are α and Tin. Economically the ammonia and the natural gas price are most influential. In comparison with grey and green ammonia, under the simulated conditions, blue hydrogen is the most cost-effective. Finally, the economic incentives through the seasonality of natural gas prices do not justify a dynamic operation of the process plant.