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Ammonia Safety
(2023)
Ammonia is an energy source that has been produced and used on a large scale for many decades, primarily as a fertilizer or feedstock in nitrogen chemistry. The CAMPFIRE alliance, founded as part of the "WIR!- Wandel durch Innovation in der Region" funding program of the German Federal Ministry of Education and Research (BMBF), aims to research and develop new energy conversion and storage technologies for the future energy system based on green ammonia. The safe handling of ammonia is an important issue along the entire value chain. Therefore, the alliance has organized a webinar to discuss the topic of ammonia safety and in particular its flammability. BAM's contribution presented the topic of flammability in detail, placed the classification of ammonia in an international, European and national context and presented the basic principles of explosion protection that result from this and must be observed during use and application.
In this study, experimental determination and modelling investigations for the explosion regions of 1,3-dioxolane/inert gas/N2O and 1,3-dioxolane/inert gas/air mixtures were carried out and compared. The experimental measurements were carried out at 338 K and atmospheric pressure according to EN1839 method T using the inert gases N2, CO2, He and Ar. The results showed that the ratio of the lower explosion limit in N2O (LELN2O) to the lower explosion limit in air (LELair) is 0.52 and the ratio of the maximum oxygen content in air (MOCair) to the limiting oxidizer fraction in nitrous oxide (LOFN2O) is 0.36 ± 0.02 independent of the inert gas. When comparing the inert gas amount at the apex based on the pure oxidizing component, which is O2 in case of air, N2O-containing mixtures need less inert gas to reach the limiting oxidizer quantity whereas the efficiency of inert gases is in the same order. The coefficients of nitrogen equivalency however were found to differ to some extent. The explosion regions of 1,3-dioxolane/inert gas/oxidizer mixtures were modelled using the calculated adiabatic flame temperature profile (CAFTP) method as well as corrected adiabatic flame temperatures. The results indicate good agreement with experimental data for CO2, N2 and Ar- containing mixtures. The noticeable deviations that occur when He is the inert gas are due to the lacking transport data of that mixture.
Most fluorinated hydrocarbons that shall replace refrigerants with high GWP, like R134a, are flammable. For evaluating inertization measures for explosion protection, flammability of low-GWP refrigerants R1234yf, R32 and R1132a blended with carbon dioxide, nitrogen and argon were studied experimentally in a closed autoclave at atmospheric conditions. Furthermore, a calculation method was adapted to reduce the experimental costs for flammability studies on these gas mixtures. For igniting R1234yf in the closed autoclave a newly developed ignition system was used that allows generating electric arcs with high ignition energy. Gas mixtures containing the mildly flammable R1234yf and R32 could be inerted by adding much less inert gas than mixtures containing R1132a, which is more similar to unfluorinated hydrocarbons regarding the explosion regions. By using the adapted model of constant adiabatic flame temperature profiles estimating the explosion limits of fluorinated hydrocarbons was possible with similar accuracy as for unfluorinated hydrocarbons.
Keywords: Explosion Protection, Inertization, Flammability, HFOs, HFC., R1234yf, R32, R1132a
The paper provides a summary of safety characteristics of hydrogen and hydrogen fuel gases. The inves-tigations focus on water electrolysis, the feeding of hydrogen into the natural gas grid and the use ofhydrogen for the fermentation process in biogas plants. The safety characteristics of hydrogen such as avery low minimum ignition energy, very large explosion range and high flame velocity with the resultingrapid pressure increase of hydrogen explosions are of particular importance for explosion protection andthey differ strongly from those of natural gas. Explosion ranges of hydrogen-methane-carbon dioxidemixtures have been measured for the use of hydrogen in biomethane production. The paper also showsand discusses explosion ranges of hydrogen and hydrogen-natural gas mixtures. Pressure and tempera-ture dependencies of the explosion limits of mixtures were investigated. Furthermore, pressure rise rates(KGvalues) were measured with regard to constructive explosion protection. The maximum experimen-tal safe gaps were determined for the classification of the mixtures and assignment to explosion groupsaccording to the European ATEX directives. It was found that admixture of 10% hydrogen to natural gashas only a minor influence on the safety characteristics of gas explosions.