Comparative Techno economic Analysis of Ammonia Electrosynthesis
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2020-01
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Abstract
Ammonia (NH3) is a valuable chemical that is used as fertilizer, antimicrobial agent, and household cleaner and is among the largest chemicals produced globally. Currently, the Haber-Bosch (H-B) process, which requires elevated pressure (~100 bar) and temperature (~450C), is used to produce the majority of NH3. The H-B generates large quantities (1500 kg-CO2/ton-NH3) of greenhouse gases (GHG), especially during the steam methane reforming process to produce hydrogen (H2) feedstock. There has been growing interest in alternative electrochemical processes for NH3 synthesis due to their modular design, reduced capital cost, and potential to reduce GHG emissions over that of the H-B process. In this thesis, six alternative NH3 electrosynthesis routes are analyzed from both economic and environmental aspects. Among the six routes, electrosynthesis of NH3 from N2 and H2O at room temperature is found to be the most economically compelling process (levelized cost ~$414/ton-NH3). Compared to a conventional H-B plant, electrosynthesis using electricity from clean sources could reduce CO2 emissions by 75-90%. Based on this analysis, we have estimated the target performance metrics that need to be achieved at scale to make the electrochemical NH3 synthesis route economically and environmentally viable. This analysis reveals that electrochemical processes have merit and potential to replace the H-B process if target performance parameters (current density higher than 400 mA/cm2, selectivity higher than 60%, energy efficiency higher than 50%, and overpotential lower than 1.5 V) are achieved. This analysis gives an early indication for the electrosynthesis route to be economically viable and environmentally sustainable as compared to the century-old H-B process.
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Wang, M. (2020). Comparative Techno economic Analysis of Ammonia Electrosynthesis (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.