Scale up and scale down issues of renewable ammonia plants: Towards modular design
2018
Sánchez, Antonio | Martín, Mariano
In this work, the scale-up and down of a renewable-based ammonia facility has been evaluated. Nitrogen is obtained from air separation. Three technologies have been compared, membrane separation, pressure swing adsorption and a Linde’s double column. Hydrogen is produced from water splitting using solar, photovoltaic, or wind energy. Finally, ammonia is synthesized in a three bed packed reactor. Two reactor designs were evaluated, direct and indirect cooling. The process is optimized by solving an NLP for each reactor design and nitrogen technology combination and for several production capacities, evaluating the operating and investment costs resulting from the need to use a number of parallel units. The production capacity defines the best technology depending on its characteristics. The results show that for very low production membranes are recommended, medium capacities should be produced using PSA while large require the use of distillation. The actual transition points have been computed. The high costs of panels and electrolyzers mitigate the issues related to duplicating small units. The expected decrease in the cost of both will result in competitive renewable ammonia production costs. Correlations for the investment and production costs as a function of the scale have been developed.
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