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Ammonia Absorbents with High Stability and High Capacity for Fast Cycling

Ammonia absorption is an alternative separation to condensation in ammonia production. Metal chloride salts selectively incorporate ammonia into their crystal lattices with remarkably high capacity. Regeneration and stability of these salts are further improved by dispersing them onto a porous silica support. Here, we discuss the optimal preparation methods of supported metal halides, as well as optimal conditions for uptake and release of ammonia. The metal halide salt particle size, support particle size, support composition and preparation methods are optimized for material stability, speed of uptake and release, and maximum ammonia capacity. An automated system was used to rapidly screen…

Paper

Comparative Technoeconomic Analysis of Conventional and Absorbent-Enhanced Ammonia Synthesis

Ammonia is the second-most produced synthetic chemical and the main precursor for nitrogen-based fertilizer. In 2015, 160 million tons were produced globally, and global demand is expected to grow 1.5% annually until 2050 [1]. However, traditional ammonia production uses natural gas or coal as its hydrogen source, and as a result, is also responsible for more than 1% of global GHG emissions and 5% of global natural gas consumption [2]. Clearly, a more sustainable ammonia production scheme is needed. One such alternative is obtain hydrogen from electrolysis powered by wind- or solar-derived electricity. It has been proposed to perform this…

Paper

Ammonia Absorption and Desorption in Ammines

While adsorption onto solids is a common separation process, absorption into solids is much less often used. The reason is that absorption is usually assumed ineffective because it includes very slow solute diffusion into the solid. An exception may be the separation of ammonia from nitrogen and hydrogen using ammines, especially at temperatures close to those used in ammonia synthesis. There, ammonia can be selectively absorbed by calcium chloride; nitrogen and hydrogen are not absorbed. The kinetics of ammonia release seem to be diffusion controlled. The kinetics of absorption are consistent with a first order reaction and diffusion in series,…

Paper

Lower Pressure Ammonia Synthesis

Ammonia is a very important chemical, mainly produced through the Haber-Bosch process. This process requires high temperature (>400 °C) and pressure (>150 bar) in order to ensure fast kinetics and high conversions, respectively.1 As a result, ammonia synthesis is known to be very complex and energy-intensive.2 To alleviate the complexity and energy requirements of ammonia synthesis, and to reduce the CO2 emissions, we are proposing an innovative reaction-absorption process to synthesize carbon-free ammonia in small plants.3 This green ammonia can be synthesized in wind-powered plants, with hydrogen from electrolysis of water and nitrogen from pressure swing adsorption of air.4 In…

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Small Scale Low-Pressure Ammonia Synthesis

Ammonia is one of the most important chemical commodities in the US 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). 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…

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Potential Strategies for Distributed, Small-Scale Sustainable Ammonia Production

Potential Strategies for Distributed, Small-Scale Sustainable Ammonia Production Alon McCormick*, Ed Cussler, Prodromos Daoutidis, Paul Dauenhauer, Lanny Schmidt, Chemical Engineering and Materials Science; Roger Ruan, Doug Tiffany, Bioproducts and Biosystems Engineering; Steve Kelley, Humphrey School of Public Affairs; Mike Reese, West Central Research and Outreach Center, University of Minnesota