Thermodynamic potential of a novel plasma-assisted sustainable process for co-production of ammonia and hydrogen with liquid metals

M.M. Sarafraz (Corresponding author), Nghiep Nam Tran, N. Pourali, E.V. Rebrov, V. Hessel

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21 Citations (Scopus)


In the present article, the thermodynamic potential of a sustainable plasma-assisted nitrogen fixation process for co-production of ammonia and hydrogen is investigated. The developed process takes advantage of chemical looping system by using a liquid metal such as gallium to drive nitrogen fixation reaction using three reactors including reactor R1 to produce gallium nitride from gallium and nitrogen, reactor R2 to produce ammonia and hydrogen from gallium nitride, and plasma reactor R3 to convert gallium oxide to pure gallium. The results of the thermodynamic assessments showed that the proposed reactions are spontaneous and feasible to occur in the reactors. Likewise, the first two reactions are exothermic with ΔH=-230[Formula presented] and ΔH=-239[Formula presented] in the reactors R1 and R2, respectively with an equilibrium chemical conversion of 100%. The plasma reactor requires thermal energy to drive an endothermic reaction of gallium oxide dissociation withΔH=+870[Formula presented]. Thermochemical equilibrium analysis showed that the molar ratio of steam to GaN, as well as the operating pressure and temperature of reactor R2 are the main operating parameters identifying the product composition in the reactor such that by increasing the temperature, the molar ratio of hydrogen to ammonia increases. However, by increasing the molar ratio of steam/GaN (φ value) from 0.1 to 1, the hydrogen content of the reactor increases from 45% to 70% at 400 °C. For φ > 1.0, the hydrogen content decreases while more hydrogen participate in the formation of NH3 thereby increasing the mole fraction of ammonia in the reactor. The equilibrium chemical conversion of all three reactors is expected to reach the completion point (χ = 100%) due to the highly negative Gibbs free energy of the liquid metal-based reactions together with a large thermal driving force supported by thermal plasma reactor. Finally, a scalability study points at a possible use of the new disruptive process design at small scale, and possible industrial transformation scenarios for a distributed production at a local site of consumption are depicted.

Original languageEnglish
Article number112709
Number of pages13
JournalEnergy Conversion and Management
Publication statusPublished - 15 Apr 2020


M. M. Sarafraz acknowledges the support provided by the University of Warwick and University of Adelaide for using software packages. N. N. Tran acknowledges a start-up fund provided by the University of Adelaide. M. M. Sarafraz, N. Pourali, E. Rebrov and V. Hessel acknowledge support from the ERC Grant Surface-COnfined fast-modulated Plasma for process and Energy intensification ( SCOPE ) from the European Commission with the grant number 810182.

FundersFunder number
Horizon 2020 Framework Programme
University of Warwick
European Commission810182
European Research Council
University of Adelaide


    • Ammonia production
    • Hydrogen production
    • Nitrogen fixation
    • Plasma reactor
    • Plasma-assisted chemical looping
    • Sustainability
    • Zero carbon process


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