(524e) Small Scale Distributed Ammonia Produced: Analysis of Pilot Plant Runs and Routes to Improve the Economics of Scale

Small Scale Distributed Ammonia Produced: Analysis of Pilot Plant Runs and Routes to Improve the Economics of Scale

Mahdi Malmali^â?¡, Michael Reese^â? , Cory Marquart^â? , Kevin Wagner^â?¡, Eric Buchanan^â? 

Alon McCormick^â?¡ and Edward L. Cussler^â?¡

^â?  West Central Research and Outreach Center

^â?¡ Department of Chemical Engineering and Materials Science

University of Minnesota, Minneapolis, MN 55455

Ammonia is one of the most important chemical commodities in the U.S. and will be a key component in helping the world meet the rising demand for food and energy. Ammonia is needed in distributed locations for agriculture (as fertilizer for small grain and corn production), for indirect hydrogen storage¹ (transported as a liquid at moderate pressure to hydrogen stations), or as a liquid fuel² (for internal combustion engines or solid oxide fuel cells). Currently, ammonia is manufactured by the Haber-Bosch process, a highly capital- and energy-intensive process requiring large quantities of fossil fuels. Ammonia synthesis is only feasible in massive centralized locations; ammonia consumption thus relies on moving anhydrous ammonia from distant locations to regions where ammonia is needed.

Recently, there has been significant effort to develop scalable technologies for conversion of intermittent energies (e.g., solar, wind) into energy dense carbon-neutral liquid fuels, and ammonia is considered to be a promising option. For the synthesis of carbon-neutral ammonia, hydrogen and nitrogen are delivered from electrolysis of water and pressure swing adsorption of air. Once produced, nitrogen and hydrogen are fed to a catalytic reactor to produce anhydrous ammonia. All these processes are carbon-free and powered by wind turbines or solar arrays.

In this talk, we are going to present a benchmark for the performance of a small-scale ammonia synthesis pilot plant powered by wind energy³. The Renewable Hydrogen and Ammonia Pilot Plant located in Morris, MN, is the first local farm-to-coop scale system for ammonia production. The energy used for this plant is stranded, located in areas far from urban centers where ammonia is primarily used as a fertilizer. This plant targets production of small amounts of ammonia for local demand, thus representing distributed production. We will present the analysis of small plant runs, along with some laboratory-scale kinetic studies, to assess the performance of different units, including reaction, phase separation and recycle. A simple but insightful model is developed, in order to understand the performance of the small-scale Haber-Bosch pilot plant and to determine the optimal conditions for operating. This model is successfully employed to predict the performance of each unit, and gives us insight into selecting appropriate unit operating conditions. Such a straightforward model may help us to understand the design of other small-scale processes in the future.

(1) Sørensen, R. Z.; Hummelshøj, J. S.; Klerke, A.; Reves, J. B.; Vegge, T.; Nørskov, J. K.; Christensen, C. H. Indirect, Reversible High-Density Hydrogen Storage in Compact Metal Ammine Salts. J. Am. Chem. Soc. 2008, 130 (27), 8660.

(2) Wojcik, A.; Middleton, H.; Damopoulos, I.; Van herle, J. Ammonia as a Fuel in Solid Oxide Fuel Cells. J. Power Sources 2003, 118 (1-2), 342.

(3) Reese, M.; Marquart, C.; Malmali, M.; Wagner, K.; Buchanan, E.; McCormick, A.; Cussler, E. L. Performance of a Small-Scale Haber Process. Ind. Eng. Chem. Res. 2016, 55 (13), 3742.