Column absorption for reproducible cyclic separation in small scale ammonia synthesis

Wagner, Kevin; Malmali, Mahdi; Smith, Collin; McCormick, Alon V.; Cussler, E. L.; Zhu, Ming; Seaton, Nicholas C.A.

doi:10.1002/aic.15685

Cited by 47 publications

(69 citation statements)

References 24 publications

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“…It has been suggested that the condensation step of the ammonia synthesis loop could be preplaced by absorption of ammonia in crystalline salts, which can absorb ammonia at partial pressures as low as 0.002 bar at moderate temperatures. [ 50–53 ] The implementation of this over the conventional condenser for separation has the potential to allow ammonia synthesis loops to operate at pressures as low as 30 bar. [ 8 ] From the thermodynamic data shown earlier, the benefits of operating at lower temperature can be seen.…”

Section: Principles Of Catalyst Mechanismmentioning

confidence: 99%

Development and Recent Progress on Ammonia Synthesis Catalysts for Haber–Bosch Process

Humphreys

Lan

Tao

2020

Adv Energy and Sustain Res

306

148

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Due to its essential use as a fertilizer, ammonia synthesis from nitrogen and hydrogen is considered to be one of the most important chemical processes of the last 100 years. Since then, an enormous amount of work has been undertaken to investigate and develop effective catalysts for this process. Although the catalytic synthesis of ammonia has been extensively studied in the last century, many new catalysts are still currently being developed to reduce the operating temperature and pressure of the process and to improve the conversion of reactants to ammonia. New catalysts for the Haber–Bosch process are the key to achieving green ammonia production in the foreseeable future. Herein, the history of ammonia synthesis catalyst development is briefly described as well as recent progress in catalyst development with the aim of building an overview of the current state of ammonia synthesis catalysts for the Haber–Bosch process. The new emerging ammonia synthesis catalysts, including electride, hydride, amide, perovskite oxide hydride/oxynitride hydride, nitride, and oxide promoted metals such as Fe, Co, and Ni, are promising alternatives to the conventional fused‐Fe and promoted‐Ru catalysts for existing ammonia synthesis plants and future distributed green ammonia synthesis based on the Haber–Bosch process.

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Section: Principles Of Catalyst Mechanismmentioning

confidence: 99%

Development and Recent Progress on Ammonia Synthesis Catalysts for Haber–Bosch Process

Humphreys

Lan

Tao

2020

Adv Energy and Sustain Res

306

148

View full text Add to dashboard Cite

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“…The absorbent synthesis has been discussed previously, where pure salts were found to have working capacities which deteriorated with cycling. 13,27 Briefly, 30 mL of ethanol and 30 mL of methanol were added to a N 2 -purged round-bottom flask along with 6 g of anhydrous MgCl 2 (98%, Sigma-Aldrich). The solution was refluxed for 1 h under N 2 purge.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Optimizing Ammonia Separation via Reactive Absorption for Sustainable Ammonia Synthesis

Kale

Ojha

Biswas

et al. 2020

ACS Appl. Energy Mater.

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Metal halide salts such as magnesium chloride have been demonstrated to be promising candidates for ammonia storage materials for energy storage and agriculture applications due to their ability to incorporate several moles of ammonia per mole of salt. Ammonia exiting a synthesis reactor can be separated from nitrogen and hydrogen by absorption into magnesium chloride. Such an absorption can be more complete and hotter than separation via ammonia condensation, the current standard in the Haber−Bosch process. Here, we discuss the optimal conditions for the cyclic uptake and release of ammonia from the supported magnesium chloride absorbents. An automated system was designed for measuring the nonequilibrium working capacity of the absorbent, as well as the impact of important operating conditions such as absorption and desorption temperature, pressure, and desorption time. Measurements of absorption and desorption kinetics provide insight into the mechanisms involved. The temperatures and pressures during absorption and desorption were designed to use minimal energy input to maximize the uptake and release of ammonia within a reasonable amount of time. In a laboratory-scale bed, absorption has a small unused bed length, so it is largely independent of mass transfer; it is dominated by how fast ammonia is fed to the bed. On the other hand, desorption is restricted both by the speed of heating the bed and by diffusion out of the absorbent. These measurements provide guidelines for ammonia separations and cycling sorbent materials on a larger scale.

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“…However, significantly reducing the pressure in the Haber-Bosch process is difficult because doing so reduces reactor single pass conversion and also requires even lower temperatures for condensation of ammonia from unreacted hydrogen and nitrogen, thus increasing refrigeration demand. An alternative approach is absorbent-enhanced ammonia synthesis in which a bed of supported alkali metal salt replaces the conventional condenser [11,12]. This absorbent allows for more complete ammonia separation as compared to condensation, and subsequently, high ammonia production rates can be achieved while operating at lower pressures [13].…”

Section: Introductionmentioning

confidence: 99%

Modeling and Optimal Design of Absorbent Enhanced Ammonia Synthesis

et al. 2018

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Synthetic ammonia produced from fossil fuels is essential for agriculture. However, the emissions-intensive nature of the Haber-Bosch process, as well as a depleting supply of these fossil fuels have motivated the production of ammonia using renewable sources of energy. Small-scale, distributed processes may better enable the use of renewables, but also result in a loss of economies of scale, so the high capital cost of the Haber-Bosch process may inhibit this paradigm shift. A process that operates at lower pressure and uses absorption rather than condensation to remove ammonia from unreacted nitrogen and hydrogen has been proposed as an alternative. In this work, a dynamic model of this absorbent-enhanced process is proposed and implemented in gPROMS ModelBuilder. This dynamic model is used to determine optimal designs of this process that minimize the 20-year net present cost at small scales of 100 kg/h to 10,000 kg/h when powered by wind energy. The capital cost of this process scales with a 0.77 capacity exponent, and at production scales below 6075 kg/h, it is less expensive than the conventional Haber-Bosch process.

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Column absorption for reproducible cyclic separation in small scale ammonia synthesis

Cited by 47 publications

References 24 publications

Development and Recent Progress on Ammonia Synthesis Catalysts for Haber–Bosch Process

Development and Recent Progress on Ammonia Synthesis Catalysts for Haber–Bosch Process

Optimizing Ammonia Separation via Reactive Absorption for Sustainable Ammonia Synthesis

Modeling and Optimal Design of Absorbent Enhanced Ammonia Synthesis

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