Process simulation of green ammonia production plant and waste heat recovery system for integration into Finnish district heating networks and energy infrastructure

An integrated process simulation model is developed to study the utilization of waste heat recovered from an industrial scale green ammonia production plant in Finland. ASPEN Plus was used to simulate the steady-state production of green hydrogen via alkaline electrolysis and it's subsequent synthesis into ammonia through the Haber Bosch process. The plant behaviour is simulated under varying power levels, hydrogen mass flow rates and district heating supply temperatures using a MATLAB code to estimate the annual hourly recoverable waste heat for two district heating networks i.e. Kokkola and Oulu in Finland. The simulations targeted an annual ammonia production of approximately 213 kt and evaluated waste heat recovery potential and district heating integration feasibility. The study reveals that the plant can generate up to 115 MW of useable waste heat, confirming its potential as a significant thermal energy source. Dynamic simulations showed seasonal variation in waste heat availability. In Oulu, a 47.16 MW district heat (DH) production system caused only 0.2% DH curtailment, while in Kokkola a 23.58 MW system resulted in 12% curtailment, highlighting the importance of site-specific, moderately sized heat pump integration for stable operation. Results indicate that although waste heat is continuously generated, its high volume relative to demand particularly during summer is limited due to feasibility constraints.