extended period also posed a challenge for the proper selection of the syngas compressor configuration. Considering the low turndown requirements for the syngas compressor over an extended period and the cost of additional power consumption in the recycle mode of operation, the cost-benefit analysis suggested using two 50% compressors. Furthermore, it was also determined that the amount of MP superheated steam
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Figure 2 Impact of different operating modes on key variables
production within the synloop will permit the operation of one 50% syngas compressor on the steam driver. This combination also provides an added flexibility in the operation with improved reliability. Challenges of synloop rerating and reconfiguration The transition of the ammonia synloop from conventional methane-based syngas – typically containing substantial levels of inert components such as argon and methane – to a stoichiometric blend of high-purity hydrogen and nitrogen introduces a suite of complex process and engineering challenges. The virtual elimination of inert materials has a significant impact on both the catalyst bed’s thermodynamic equilibrium and kinetics, as well as the overall hydraulic assessment of the synloop. Change in the circulation rate impacts heat exchanger duties, system pressure drops, and the turndown capability of syngas compressors. Elevated reactant partial pressures in the feed stream shift the equilibrium conversion, enhancing ammonia yield per pass. However, this gain also requires recalibration of the reactor temperature profile and rerating to mitigate risks such as catalyst sintering or localised hotspots. A thorough evaluation of
equilibrium and kinetics performance, hydraulics of the synloop, and the mechanical integrity of existing equipment – originally engineered for higher inert dilution and different gas compositions – is essential. KPI undertook a comprehensive rerating of the entire synloop across all projected operating scenarios, including a detailed kinetics assessment of the converter beds. This resulted in the optimisation of critical operating parameters, including inert concentration, pressure, circulation rate, bed temperature profiles, pressure drop behaviour, heat exchanger loads, and compressor performance (for both syngas and ammonia services). Catalyst bed profiles were further validated through collaboration with all major catalyst suppliers to ensure the desired temperature profiles and ammonia production rates were achievable. Key variables – including inert levels, circulation rate, ammonia conversion, and operating/pressure drop characteristics – were mapped across both normal and turndown modes for clean ammonia production and benchmarked against baseline grey ammonia operations, as shown in Figure 2 . In addition to process refinements, the configuration was adapted to accommodate superheated steam generation for the
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