(486c) Scale up and Scale Down Issues of Renewable Ammonia Plants: Towards Modular Design
Large ammonia plants based on fossil resources dominate industry (Appl, 2011). It is a power demanding industry. However, nitrogen and hydrogen can be produced from renewable sources (Sánchez and Martín, 2018). In this work, a process level analysis for the optimal use of distributed sources of energy at various scales applied to the production of ammonia is performed. The scale up and down of facilities is evaluated selecting the proper technology for each of the three sections of the plant, evaluating the technologies and their economics. The facility consists of four stages, power collection, considering wind turbines or solar PV panels, air separation for which membranes, PSA or distillation technologies are evaluated, water electrolysis and ammonia synthesis evaluating two reactor designs. The process is optimized by solving a MINLP for several production capacities evaluating the operating and investment costs resulting from the need to use a number of parallel units membranes and PSA systems.
The production capacity defines the best technology depending on its characteristics. A number of trade-offs are seen in the results. While membranes are suitable for very small production capacities, PSA system for medium and distillation column for large, PSA systems are competitive across scales, but the large number of units required can be a drawback to pursue this technology that requires lower operating pressure than distillation columns. Modular designs are only efficient and competitive, in economic terms, when full capacity is used, however this design presents other benefits have been not evaluated, for example, are versatile in their operation. The large energy consumption has larger impact in the investment of large facilities, where energy collecting units represent 60% of the production costs. However, smaller capacities investment cost is governed by chemical units. Finally, the expected decrease in PV panels is far larger than that of wind turbines, representing 90% savings in PV panels and very promising production costs for ammonia below 1â¬/kg. These saving can reduce the investment cost by half in the near future.
Environmental Protection Agency (EPA), 2017. Distributed generation of electricity and its environmental impacts https://www.epa.gov/energy/distributed-generation-electricity-and-its-environmental-impacts Last accessed: February, 2018.
Pepermans, G., Driese, J., Haeseldonckx, D., Belmans, R., Dâhaeseleer, W.D., 2005. Distributed generation: Definition, beneficts and issues. Energy Policy, 33 (6), 787-798.
Baldea, M., Edgar, T.F., Stanley, B.L., Kiss, A.A., 2017. Modular manufacturing processes. Status, challenges and opportunities. AIChE J., 63 (10), 4262-4272.
SÃ¡nchez, A., MartÃn, M., 2018. Optimal renewable production of ammonia from water and air. J. Clean. Prod., 178, 325-342.
Appl M (2011) Ammonia 2.- Production processes. Ullmannâs Encyclopedia of industrial chemistry. DOI: 10.1002/14356007.o02_o11