Halogen atmospheres, combustion

There have been far more thermochemical experiments carried out in fluorine than in any other halogen atmosphere, the large majority of them by fluorine bomb calorimetry [110-116]. Thus, only fluorine combustion calorimetry will be covered in this section with a strong emphasis on bomb calorimetry. Note, however, that many technical details and safety precautions mentioned here for fluorine combustion calorimetry also apply to combustion in other halogens. 

Halogen content represents an upper limit for combustion of a high-halogen coal in a salty (marine location) atmosphere. For typical low-halogen U. S. coals, the chloride concentration would be v 0.01 mol % and the NaCl pressures correspondingly less. 

The next chapter reviews the reactions of free atoms and radicals which play an important role in the modeling of complex processes occurring in the polluted atmosphere and in combustion chemistry. J. Jodkowski discusses the computational models of the reaction rate theory most frequently used in the theoretical analysis of gas-phase reaction kinetics and presents examples of the reactions of reactive components of the polluted atmosphere, such as 02, NOx, OH, NH2, alkyl radicals, and halogen atoms. Kinetic parameters of the reactions under investigation are provided in an analytical form convenient for kinetic modeling studies. The presented expressions allow for a successful description of the kinetics of the reaction systems in a wide temperature range and could be used in kinetic studies of related species. 

Atmospheric halogen compounds (Penkett, 1982) are of both natural and industrial origin. Probably the most abundant halocarbon in the troposphere is methyl chloride, CH3CI, which is present at a level of 0.6-2 parts in 10 . It appears to be present in volcanic emissions, formed by microbial fermentation, by the combustion of vegetation (Lovelock, 1975), and by the SN2 reaction of methyl iodide (a constituent of marine algae) with the large excess of chloride ion in seawater (Zafiriou,... 

The combustion reaction can be prevented by depletion of the oxidant, one of the three essential components making up the fire triangle. This forms the basis of inert gas blanketing in which the oxygen is replaced by an inert gas such as nitrogen, carbon dioxide or a halogenated hydrocarbon. By adequate depletion of oxygen, the atmosphere will be rendered non-flammable irrespective of the concentration of combustible material. 

---