Session: 04-03: SMRs, Advanced Reactors and Fusion

Paper Number: 147514

147514 - Modeling of Carbon-Free Ammonia Plants Powered by Small Modular Reactors 

Abstract: 

Globally, 43% of annual hydrogen production was used for ammonia production in 2018. As a result, ammonia production accounts for 2% of global fossil energy use and 1.2% of global GHG emissions. Given that 80% of ammonia produced today is used in fertilizers such as urea and ammonium nitrate, a significant production increase of ammonia is expected with the growing population. Thus, decarbonizing the existing ammonia market represents a large opportunity for carbon-free ammonia to significantly reduce global GHG emissions. Leveraging its simplicity and cost advantages, small modular reactors (SMR) are in the position to help the energy-intensive ammonia production industry reduce carbon emissions. Moreover, being increasingly considered as an energy vector, ammonia has significant advantages over hydrogen in terms of the cost of storage and transportation. Thus, we expect carbon-free ammonia will play a key role in enabling carbon-free hydrogen. The presentation will provide an overview of the green ammonia project funded by the US Department of Energy and discuss some of the preliminary modeling work completed using Aspen Plus. The goal of this project is to develop integrated efficient designs for carbon-free ammonia plants. One design uses freshwater as the source of hydrogen, while the other design uses seawater (or brackish water) as the source. This project provides an opportunity to demonstrate examples of SMR-powered integrated energy systems (IES) for carbon-free ammonia production. In both designs, a NuScale SMR  (VOYGR^TM-6 plant) is used as the primary energy source providing both electricity and steam for the plants. While low-temperature electrolysis technologies exist for green hydrogen production, including alkaline and PEM electrolyzers, high-temperature electrolyzer holds some promise for higher energy efficiency and lower cost for hydrogen. Thus, the current work is focused on a high-temperature steam electrolyzer (HTSE) utilizing solid oxide electrolysis cells (SOEC). In this work, the designed SOEC stack temperature is 800 ℃ to reach attractive energy density. Compared to low-temperature electrolyzers, the HTSE system requires a substantial amount of thermal energy to generate superheated steam for the electrolysis process. This is where nuclear energy systems can outperform renewable energies such as wind and solar for cost-effective hydrogen production. For a given power input, current density, and steam utilization rate, the SOEC stack model calculates the Nernst potentials and operating voltage of the cell. In addition, the model predicts the stack efficiency and molar flow rates of steam, hydrogen, and oxygen. To assist techno-economic analysis, the stack model can also consider potential stack degradation that will affect the activation voltage and ohmic losses, both of which are commonly represented using area-specific resistance (ASR). Moreover, the talk will discuss the Haber-Bosch model for ammonia synthesis and how each of the subsystems can be integrated to achieve higher plant efficiency and productivity.

Presenting Author: Hailei Wang Utah State University

Presenting Author Biography: Dr. Hailei Wang is an Assistant Professor in the Mechanical and Aerospace Engineering Department at Utah State University and the Director of the Energy Technology Research & Innovation (eTRI) Lab. He has broad research expertise in heat transfer and advanced energy system modeling. His work has been funded by various agencies including the NRC, DOD, and several DOE offices such as the Office of Nuclear Energy, Solar Energy Technology Office, ARPA-E, Building Technology Office, and Hydrogen and Fuel Cell Program. His energy system research and thermal modeling work has also been supported by various corporations including Cummins, Medtronic, Thermo Fisher, and NuScale Power. He has published over 60 journal and conference papers and holds three granted patents and multiple patent applications.

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