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Hydrogen is a carbon-free fuel and can be expected to play a significant role in the global clean energy transition. In this study, two proposed small-scale hydrogen production plant configurations were designed and simulated for high-purity hydrogen production at a rate of 25 kg H2 /day. The feasibility and economic viability of the proposed plant configurations were examined. Additionally, the performance and sensitivity analysis were assessed under different operating conditions. Configuration A proposed to use two reactors for ammonia cracking and H 2 separation, respectively. Configuration B considers that the decomposition of ammonia and H 2 separation simultaneously occurs in a single integrated reactor. Despite the configuration B was more energy efficient than configuration A but both configurations are applicable. The total H 2 production cost of configuration A was 6.39 $/kg H2 and that of configuration B was 6.06 $/kg H2. Since the proposed plant configurations generated both hydrogen and nitrogen, the total cost of production was distributed between them. Therefore, the final H 2 and N 2 separation costs of configuration A was 5.05 $/kg H2 and 1.14 $/kg N2 , and configuration B was 4.72 $/kg H2 and 1.08 $/kg N2. The hydrogen production cost from different ammonia synthesis pathways was compared. The technology readiness level (TRL) for hydrogen production from ammonia cracking was assessed and identified at a range of TRL 4–6. It can also be considered that the ammonia synthesis pathway controlled the ammonia prices and subsequently the hydrogen production cost. • Two proposed configurations were designed for H 2 production from blue NH 3. • Techno-economic assessment was performed for small-scale H 2 plants. • The final H 2 cost of proposed configuration A was higher than configuration B. • The H 2 production cost from different NH 3 synthesis pathways was also compared. • The pathway of NH 3 synthesis influenced the prices of NH 3 and H 2. [ABSTRACT FROM AUTHOR]

The interest in nonthermal discharge plasma has recently increased over the last few decades due to the ability to generate new radicals at atmospheric pressure. This paper presents a comprehensive analysis of the dissociation processes and reaction rates of various water vapour samples by dielectric barrier discharge plasma (DBD). The influence of water contamination and the presence of ammonia (NH 3) on hydrogen production from water vapour was investigated. A novel reaction rate expression was proposed to fit the plasma-water vapour experiment results. The hydrogen production and conversion rate of pure reverse osmosis (RO) water samples showed greater results than the contaminated water samples in all experiments at different tested bubbling temperatures. The higher conversion rate was obtained from RO water combined with 1%NH 3 at a bubbling temperature of 50 °C and was 1.17%. The water contamination influenced the generated DBD plasma micro discharges, consequently decreasing the electron collisions, leading to lower water vapour conversion into constituent elements H 2 and O 2. It was also found that the influence of ammonia on the water vapour decomposition was related to the NH 3 concentration. Moreover, the reaction rate showed good agreement with the experimental results. It was observed that the energy efficiencies were obtained at an operating temperature of 50 °C for pure RO, GTW, and CTW water samples enhanced by adding 1%NH 3 , for example, the RO energy efficiency value at a bubbling temperature of 50 °C increased from 0.133% to 1.15% because of more hydrogen was generated. It implies that the water vapour decomposition processes are influenced by the following parameters: input gas temperature, reaction time, plasma power, oven or reactor heating temperature, the separation method, sampling method, and sampling collection time. [Display omitted] • The hydrogen production from various water types by DBD plasma is investigated. • The presence of ammonia enhanced the hydrogen production of water vapour. • The water contamination has a negative effect on the plasma water decomposition. • The new rate equation showed a good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Water recovery from Pt/Al2O3 catalyst combustion assisted by hydrogen is studied in two different systems. The hydrogen conversion rate and the resulting Pt-catalyst combustion temperature are measured over the reaction time. The Pt-catalyst combustion experiment is also performed using the hydrogen and oxygen produced by a PEM water electrolyzer. The recovered water is compared with the acceptable levels of elements in drinking water as defined by the World Health Organization (WHO). The hydrogen conversion rate reaches 100% after 20 min, and the maximum temperature increases with an increased H2/air feeding flow rate. Ion chromatographic analysis of the water resulting from the H2/air mixture contains four species (Li+, NH4+, K+, NO2−) with concentrations higher than the WHO standards. Moreover, the cation and anion analyses of the Pt-catalyst combustion using the PEM water electrolysis experiment agree with the WHO standards, except for lithium. [ABSTRACT FROM AUTHOR]

Ammonia radical injection using pulsed dielectric barrier discharge (DBD) plasma has been investigated as a means to control NOx emissions from combustors. When DBD plasma-generated radicals ([NH.sub.2], NH, N, and H) are injected into a flue gas containing nitrogen oxide (NOx), NOx is removed efficiently by chain reactions in the gas phase. However, because the percentage of NOx removal gradually decreases with increasing oxygen concentrations beyond 1% [O.sub.2], improvement of the DeNox (removal of nitrogen oxide) characteristics at high [O.sub.2] concentrations was necessary for commercial combustors. A two-staged injection of the DeNox agent was developed based on the detailed mechanisms of electron impact reactions and gas phase reactions. A concentration of H radical was observed to play an important role in N[O.sub.x] formation and removal. The effects of applied voltages, oxygen concentrations, and reaction temperatures on N[O.sub.x] removal were investigated under normal and staged injection. N[O.sub.x] removal was improved by approximately 20% using staged injection at [O.sub.2] concentrations of I to 4%. Index Terms--Dielectric barrier discharge, nitrogen oxide, DeNOx, ammonia, oxygen, radical injection.

Ammonia radicals are produced by a dielectric barrier discharge (DBD) in a chamber, called radical injector, which is separate from the chamber that NO gas flows. The radicals are injected into the mixing zone in NO gas flow field to decompose NO gas. The power source for generating the DBD is a one cycle sinusoidal (OCS) waveform so as to easily control the electrical power consumed in the DBD plasma. The fundamental frequency of the OCS power source is 150 kHz. Based on the molar ratio of ammonia particles to NO particles in a unit time, NO removal characteristics were discussed. By increasing the DBD consumed energy, the molar ratio approaches 1 showing the stoichiometric DeNO by N[H.sub.2] radicals. A high energy efficiency is found by reducing the consumed energy in the radical injector, where the molar ratio is higher than 1. In this case, the excess ammonia gas without converting into ammonia radicals in the radical injector is directly injected into the reaction zone, and contributes to decompose the NO gas. Oxygen gases with a concentration from 5% to 15% included in the NO gas significantly contribute to decompose NO gases, which brings a decomposition of NO with a low molar ratio. Index Terms--NO removal, dielectric barrier discharge, intermittent discharge, nonthermal plasma.