On the Possibility of Reducing Explosion Hazard of Gas Mixtures through the Use of the Fluorinated Phlegmatizers


Annotation:

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.

References:
1. General rules of explosion safety for explosion and fire hazardous chemical, petrochemical and oil refining plants: Federal rules and regulations in the field of industrial safety. Ser. 09. Iss. 37. Moscow: ZAO NTTs PB, 2017. 130 p. (In Russ.).
2. Catsoniddes J.C., Andrews G.A., Phylactou H.H., Chattaway A. Fluorinated halon replacemet agentsin explosion inerting. Journal of Loss Prevention in the Process Industries. 2015. Vol. 36. № 6. pp. 544–552.
3. Lisochkin Ya.A., Poznyak V.I. Assessment of the explosiveness of fluorine-containing monomers and their mixtures on minimum ignition pressure at the fixed ignition energy. Fizika goreniya i vzryva = Physics of combustion and explosion. 2006. № 2. pp. 19–22. (In Russ.).
4. Kopylov S.N., Koltsov S.A. Mechanism of destruction of the fluorinated hydrocarbons in the flame. Pozharnaya bezopasnost = Fire safety. 2005. № 2. pp. 56–62. (In Russ.).
5. Pagliaro J.L., Linteris G.T., Babushok V.I. Premixed flame inhibition by C2HF3Cl2 and C2HF5. Combustion and Flame. 2016. № 1. pp. 54–65.
6. Pagliaro J.L., Linteris G.T., Sunderland P.B., Baker P.T. Combustion inhibition and enhancement of premixed methane-air flames by halon replacements. Combustion and Flame. 2015. № 1. pp. 41–49.
7. Zhang K., Meng X., Wu J. Flammability limits of binary mixtures of dimethyl ether with diluent gases. Journal of Loss Prevention in the Process Industries. 2014. № 3. pp. 138–143.
8. Babushok V.I., Linteris G.T., Baker P.T. Influence of water vapor on hydrocarbon combustion in the presence of hydrofluorocarbon agents. Combustion and Flame. 2015. № 5. pp. 2307–2310.
9. Shebeko Yu.N., Shebeko A.Yu., Azatyan V.V., Navzenya V.Yu. On inhibition and promotion of methane combustion by fluorinated hydrocarbons in oxidizers with different oxygen content. Proceedings of the Sixth International Seminar on Fire and Explosion Hazards. Leeds: Research Publishing, 2010. pp. 621–631.
10. Azatyan V.V., Shebeko Yu.N., Shebeko A.Yu., Navtsenya V.Yu. On promotion and inhibition by fluorinated hydrocarbons of methane burning in oxidizing environments with different oxygen content. Khimicheskaya fizika = Chemical physics. 2010. № 9. pp. 42–51. (In Russ.).
11. Azatyan V.V., Shebeko Yu.N., Navtsenya V.Yu., Kopylov S.N., Shebeko D.Yu., Zamyshlevskiy E.D. Influence of halocarbons on combustion characteristics of gas-air mixtures in the closed vessel. Pozharovzryvobezopasnost = Fire and explosion safety. 1998. № 3. pp. 8–18. (In Russ.).
12. GOST 12.3.047—2012. Occupational Safety Standards System. Fire safety of technological processes. General requirements. Methods of control. Available at: http://docs.cntd.ru/document/1200103505 (accessed: January 16, 2019). (In Russ.).
DOI: 10.24000/0409-2961-2019-2-20-24
Year: 2019
Issue num: February
Keywords : near-stoichiometric mixtures near-limit mixtures oxidizing environment maximum explosion pressure maximum explosion pressure rising velocity normal burning velocity
Authors:
  • Shebeko A.Yu.
    Shebeko A.Yu.
    Cand. Sci. (Eng.), Department Head, ay_shebeko@mail.ru FGBU VNIIPO of EMERCOM of Russia, Balashikha, Russia