Fluorinated phlegmatizers are related to one of the most advanced fire extinguishing means. These substances started using for the phlegmatization (permanent or emergency) of gas mixtures formed at the production facilities as a result of accidents. At the same time, there is no enough data in the literature that allow to implement this method of explosion protection. This is especially related to the case when the oxygen content in the oxidizing environment and in the air varies. Experimental studies have been carried out on the possibility of reducing the explosion hazard of gas mixtures of the following types: flammable gas — oxidizing medium — fluorinated phlegmatizer of near-stoichiometric composition. In this case, under the near-stoichiometric composition the gas mixture is understood that corresponds to complete combustion of the original fuel only (methane, hydrogen) up to the carbon dioxide (CO2) and water vapor (H2O), without considering possible participation of fluorinated phlegmatizers in the flame propagation processes. The oxidizing environment was a mixture of nitrogen and oxygen with the content of the latter in the oxidizing environment 15, 20.6 (air) and 25 % vol. Trifluoromethane, pentafluoroethane and perfluorobutane were investigated as the fluorinated phlegmatizers. Maximum explosion pressure, maximum explosion pressure rising, maximum velocity of explosion pressure rising, and the normal rate of combustion are measured. It was revealed that the fluorinated phlegmatizers can manifest both inhibitory and promoting effects. The inhibitory effect is expressed in the monotonous decrease in maximum velocity of explosion pressure rising and the normal rate of combustion at increase of the concentration of phlegmatizers in the investigated mixtures, while the promoting effect is described by the presence of maxima in the dependences of the maximum explosion pressure on the phlegmatizers concentration. In this case, the dependences of the investigated indicators of explosion and fire hazard on the phlegmatizers concentration are qualitatively similar for the cases of methane and hydrogen burning. Qualitative explanation is proposed for the observed effect of promoting combustion of near-stoichiometric mixtures of methane and hydrogen with fluorinated phlegmatizers based on the possibility of additional heat release in the flame front. Comparison was made with the case of the effect of the fluorinated phlegmatizers on the near-limit mixtures, which showed significantly different character of influence for the near-limit mixtures. The obtained results can be used at designing the explosion protection systems of the technological processes at the enterprises of chemical, petrochemical and refining industries.
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