Ammonia can be synthesized at low pressure by the use of an ammonia selective absorbent. The process can be driven with wind energy, available locally in areas requiring ammonia for synthetic fertilizer. Such wind energy is often called "stranded," because it is only available far from population centers where it can be directly used. In the proposed low pressure process, nitrogen is made from air using pressure swing absorption, and hydrogen is produced by electrolysis of water. While these gases can react at approximately 400 °C in the presence of a promoted conventional catalyst, the conversion is often limited by the reverse reaction, which makes this reaction only feasible at high pressures. This limitation can be removed by absorption on an ammine-like calcium or magnesium chloride. Such alkaline metal halides can effectively remove ammonia, thus suppressing the equilibrium constraints of the reaction. In the proposed absorption-enhanced ammonia synthesis process, the rate of reaction may then be controlled not by the chemical kinetics nor the absorption rates, but by the rate of the recycle of unreacted gases. The results compare favorably with ammonia made from a conventional small scale Haber-Bosch process.
Bibliographical noteFunding Information:
This work was primarily supported by ARPA-E, a part of the US Department of Energy, by the Minnesota Environment and Natural Resources Trust Fund, as recommended the Legislative-Citizen Commission on Minnesota Resources, and by MNDRIVE, an initiative of the University of Minnesota. Additional support came from the Dreyfus Foundation.
© 2017 Journal of Visualized Experiments.
- Ammonia synthesis
- Distributed manufacturing
- Issue 126
- Low pressure
- Small scale
- Stranded energy
- Sustainable process
- Wind energy