Exergy analysis of industrial ammonia synthesis

Kirova-Yordanova, Zornitza

doi:10.1016/j.energy.2004.03.036

Cited by 72 publications

(53 citation statements)

References 3 publications

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“…Both these processes require a major input of energy, either in the form of heat or electricity, and consequently cause a significant concomitant pollution derived from the combustion of fossil fuels for heat and electricity generation. The total energy requirement is in the range 28-166 GJ t 21 NH 3 [7,15]. Furthermore, the severe process conditions require sophisticated high-pressure and high-temperature machinery that is operated in large-scale centralized plants producing typically 1000-3000 t NH 3 day 21 [7,17].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, NH 3 may find application as a hydrogen carrier [9,10] and as a fuel for alkaline fuel cells [11,12] and in internal combustion engines [13,14] (http://nh3fuelassociation.org/2013/06/20/the-amveh-an-ammoniafueled-car-from-south-korea/). Currently, NH 3 is produced industrially from N 2 and H 2 via the catalytic Haber-Bosch process at up to 300 bar and 400-5008C [7,[15][16][17][18]. The overall process is characterized by the high energy consumption associated with the production of the reactants.…”

Section: Introductionmentioning

confidence: 99%

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Rational design of metal nitride redox materials for solar-driven ammonia synthesis

2015

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Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH 3 ) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH 3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH 3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700–1200°C that yields NH 3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rational design of metal nitride redox materials for solar-driven ammonia synthesis

2015

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“…This limits their attractiveness for the proposed concept since this energy can not be easily integrated at the higher temperatures required for the endothermic oxide reduction step. On the other hand, binary transition metal nitrides with relatively high NH 3 equilibrium yields (e.g., Mn 4 Although well-studied for their refractory properties 32,33 hydrolysis of nitrides and NH 3 formation kinetics have been rarely reported 27,[34][35][36] . Pourbaix diagrams providing information on corrosion mechanisms are typically only available for pure elements 37 .…”

Section: Materials Composition Determining Energy Conversion Efficienmentioning

confidence: 99%

“…Approximately 45% of the global H 2 production is absorbed as feedstock in the synthesis of NH 3 6 . The H 2 feedstock is generated on-site from fossil resources (mainly natural gas, coal or Naphtha), leading to significant fossilbased CO 2 emissions 4 and production of NH 3 in a few hundred large-scale centralized facilities world-wide 7 . Given the increasing global population and the potential of NH 3 as a "perfect hydrogen carrier" 8,9 and as a convenient alternative fuel in compression-ignition engines 10,11 , direct synthesis of NH 3 from N 2 , H 2 O and sunlight may contribute to a sustainable solution to two of our most demanding challenges, energy and food.…”

Section: Introductionmentioning

confidence: 99%

“…Global production of NH 3 is currently about 130 million metric tons (t) annually 3 . Ammonia is produced industrially via heterogeneous catalysis that cleaves N 2 and hydrogenates nitrogen to NH 3 in a single step conducted at some of the most severe conditions in the chemical industry of up to 30 MPa and 500°C 4 . The compression work required for the technically sophisticated synthesis accounts for about 16% of the 28-37 GJ t -1 NH 3 consumed by the process 5 .…”

Section: Introductionmentioning

confidence: 99%

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An Ionicity Rationale to Design Solid phase Metal Nitride Reactants for Solar Ammonia Production

Michalsky

Pfromm

2012

J. Phys. Chem. C

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Ammonia provides the basis of nutrition for a large portion of the human population on earth and could be used additionally as a convenient hydrogen carrier. This work studies a solar thermochemical reaction cycle that separates the reductive N2 cleavage from the hydrogenation of nitrogen ions to NH3 without using electricity or fossil fuel. The hydrolysis of binary metal nitrides of magnesium, aluminum, calcium, chromium, manganese, zinc, or molybdenum at 0.1 MPa and 200–1000 °C recovered up to 100 mol % of the lattice nitrogen with up to 69.9 mol % as NH3 liberated at rates of up to 1.45 × 10–3 mol NH3 (mol metal)−1 s–1 for ionic nitrides. These rates and recoveries are encouraging when extrapolated to a full scale process. However, nitrides with lower ionicity are attractive due to simplified reduction conditions to recycle the oxidized reactant after NH3 formation. For these materials diffusion in the solid limits the rate of NH3 liberation. The nitride ionicity (9.96–68.83% relative to an ideal ionic solid) was found to correlate with the diffusion constants (6.56 × 10–14 to 4.05 × 10–7 cm2 s–1) suggesting that the reduction of H2O over nitrides yielding NH3 is governed by the activity of the lattice nitrogen or ion vacancies, respectively. The ionicity appears to be a useful rationale when developing an atomic-scale understanding of the solid-state reaction mechanism and when designing prospectively optimized ternary nitrides for producing NH3 more sustainably and at mild conditions compared to the Haber Bosch process.

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Thermodynamics of metal reactants for ammonia synthesis from steam, nitrogen and biomass at atmospheric pressure

Michalsky

Pfromm

2011

AIChE Journal

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Catalytic ammonia synthesis at approximately 30 MPa and 800 K consumes about 5% of the global annual natural gas production causing significant CO2 emissions. A conceptual solar thermochemical reaction cycle to produce NH3 at near atmospheric pressure without natural gas is explored here and compared to solar thermochemical steam/air reforming to provide H2 used in the Haber‐Bosch process for NH3 synthesis. Mapping of Gibbs free energy planes quantifies the tradeoff between the yield of N2 reduction via metal nitridation, and NH3 liberation via steam hydrolysis vs. the temperatures required for reactant recovery from undesirably stable metal oxides. Equilibrium composition simulations suggest that reactants combining an ionic nitride‐forming element (e.g., Mg or Ce) with a transition metal (e.g., MgCr2O4, MgFe2O4, or MgMoO4) may enable the concept near 0.1 MPa (at maximum 64 mol % yield of Mg3N2 through nitridation of MgFe2O4 at 1,300 K, and 72 mol % of the nitrogen in Mg3N2 as NH3 during hydrolysis at 500 K). © 2011 American Institute of Chemical Engineers AIChE J, 58: 3203–3213, 2012

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Exergy analysis of industrial ammonia synthesis

Cited by 72 publications

References 3 publications

Rational design of metal nitride redox materials for solar-driven ammonia synthesis

Rational design of metal nitride redox materials for solar-driven ammonia synthesis

An Ionicity Rationale to Design Solid phase Metal Nitride Reactants for Solar Ammonia Production

Thermodynamics of metal reactants for ammonia synthesis from steam, nitrogen and biomass at atmospheric pressure

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