Impact on greenhouse gas emissions in the ammonia production process by reusing heat in the CO2 absorption stage

Ammonia production is one of the largest contributors to greenhouse gas emissions in the chemical industry, generating 2.4 tonnes of CO₂ per tonne of product and requiring an energy intensity of 46 GJ/t (IEA-2021). In 2020, 50% of the natural gas and 44% of the coal used by the global chemical industry went to the ammonia chain (IEA-2021). The hydrogen used in the synthesis of ammonia must be purified to remove the CO₂ generated during the steam reforming process of natural gas or coal gasification. This work focuses on the gaseous absorption of CO₂ to reduce the absorption temperature and the heat required for the regeneration of the absorbent solution. Using simulations in HYSYS® and experimental design, the potential for reducing energy consumption and heat recovery was evaluated, aiming to remove more than 90% of the CO₂. The results demonstrated CO₂ removal efficiencies between 85% and 99%, with a heat recovery potential equivalent to 2.32 GJ per tonne of ammonia produced. Such energy recovery corresponds to a 5% reduction in the energy intensity of ammonia production, compared to data from the International Energy Agency (IEA-2021). These results reveal an opportunity for more sustainable processes in the global ammonia industry.