Hydrogen faces challenges in transportation and storage due to its low volumetric energy density, the need for high-pressure or cryogenic storage, and its flammability. Ammonia is therefore considered a promising hydrogen carrier because of its high hydrogen content and relatively convenient storage and transportation. Currently, hydrogen production from ammonia is mainly based on catalytic thermal cracking, in which catalysts enhance ammonia conversion at relatively low temperatures. However, previous studies have largely focused on catalyst development, reactor design, and pilot-scale ammonia cracking systems, while the application of MILD combustion to industrial-scale ammonia cracking furnaces remains limited. This study numerically investigated the effects of methane MILD combustion on the thermal characteristics, emissions, and ammonia cracking efficiency of an industrial-scale ammonia cracking furnace equipped with Ni-based catalysts. The effects of varying the flue gas recirculation ratio and preheating temperature on furnace performance were evaluated. Compared with conventional combustion, MILD combustion produced a more uniform temperature distribution, reducing hot spots and improving the thermal conditions of the reforming tubes. Increasing the preheating temperature of the flue gas–air mixture reduced CO emissions while increasing the reforming tube temperature and ammonia cracking efficiency. At a flue gas–air mixture temperature of approximately 1250 K, low CO emissions, stable thermal conditions in the reforming tubes, and high ammonia cracking efficiency were achieved. These results demonstrate the potential of MILD combustion for achieving stable and efficient operation of industrial-scale ammonia cracking furnaces.
 

Moderate or Intense Low-oxygen Dilution (MILD), ammonia cracking, hydrogen