Dynamic Simulation of Green Ammonia Synthesis Plant

The carbon emissions from human activities are causing significant harm to the planet, leading to increased temperatures, melting of polar ice caps, rising sea levels, and other negative impacts on the environment. One promising solution is the use of green hydrogen as a fuel source, which could have a much lower carbon footprint than traditional fossil fuels. The production of hydrogen can be achieved through various methods, including the electrolysis of water, which splits water molecules into hydrogen and oxygen. To mitigate these effects and ensure a sustainable future, countries are taking various measures to reduce their carbon footprint, including increasing the use of clean energy sources and improving energy efficiency. Hydrogen storage and transportation pose major challenges since it is the one of the lightest gases leading to low energy densities.Ammonia is emerging as a hydrogen carrier due to its high gravimetric storage densities of hydrogen. It is produced through the combination of hydrogen and nitrogen using the Haber-Bosch process. Ammonia can then be used as a clean and efficient fuel for various applications, such as transportation and power generation. Fluctuations in the hydrogen feed flow rate, resulting from variations in renewable energy sources can significantly impact the pressure and operating temperature within the system.}Morocco holds significant potential for renewable energy development due to its favorable geographic location and natural resources. The geographic location situated close to Europe makes Morocco well positioned for exporting green hydrogen to European markets. The chosen location for the ammonia plant is Boujdour in Morocco due to its excellent wind capacity factor of 67%.Modern ammonia production plants employ control systems to maintain stable pressure. When there is a reduction in hydrogen feed flow rate, these reductions result in severe pressure reductions which would lead to metal fatigue and damage the entire production unit. Hence, these control systems respond by adjusting parameters to sustain pressure within the system. Aspen Plus Dynamics has been used in the present thesis work to model the dynamics of the ammonia synthesis plant. The varying hydrogen feed flow rate is a consequence of renewable energy fluctuations, which is served as the basis for modeling three distinct scenarios involving a 20%, 50%, and 70% reduction in hydrogen feed flow rate. Three distinct control strategies were developed where each control strategy, based on controlling the cooling duty of the condenser, manipulating the brake power of the recycle compressor, and regulating the nitrogen feed flow rate, demonstrated effective stabilization of the system's pressure, even during dynamically changing input conditions. Both linear and step reduction in hydrogen feed flow rate have been considered to gain understanding of the dynamic the behaviour of the system.Significant outcomes were found when a reduction in hydrogen feed flow rate is imposed on all three control strategies. For a 20% reduction in hydrogen feed flow rate, the condenser's duty reduced from -1.2 MW to -1.05 MW, while the brake power of recycle compressor reduced from 12.5 kW to 5.5 kW. Furthermore, the stoichiometric ratio of H2:N2 changed from 3 to 2.8. These changes successfully stabilized the pressure in the ammonia synthesis plant under varying hydrogen input flow rate...Mechanical Engineering | Energy, Flow and Process Technolog