The isothermal design concept for ammonia synthesis
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If the ruthenium-based catalyst experiments are successful, the design pressure for ammonia synthesis will drop below 10. MPa, and the activation temperature of the catalyst will be below 260°C. In this case, ammonia synthesis plants will be able to operate using an 8.0 MPa methanol-based design scheme. Everyone is welcome to share their opinions!
It doesn’t seem that simple; one can refer to Professor Liu Huazhang’s article from Zhejiang University of Technology titled “Several Issues in the Industrialization of Ruthenium-Based Ammonia Synthesis Catalysts”
Based on my preliminary estimates, the industrialized approach might involve a pressure of 10 MPa; the compressor structure could be simplified. The space velocity would be 10,000, with a hydrogen-to-nitrogen ratio of 2 and 5% inert gas. A membrane separation unit or cryogenic device could be used in the synthesis circuit for hydrogen extraction. The ammonia synthesis tower would have one axis and three diameters: iron catalysts would be used in the first and second stages, while ruthenium catalysts would be used in the third and fourth stages. Heat exchange would occur between the outlets of the first and second stages, the outlet of the third stage would be cooled, and the outlet of the fourth stage would go directly into the direct-fired waste heat boiler without any cooling. The ammonia content at the outlet would be greater than 20%. This approach allows for full utilization of the properties of ruthenium catalysts, and the existing engineering capabilities in this industry are sufficient to implement it, without introducing excessive risks due to too many changes
Has the experiment been successful now? Do any manufacturers use it?
Modern large-scale ammonia synthesis plants basically do not use inert gases, and therefore do not require hydrogen recovery systems