Analysis and Disposal of Fluorine

Abstract

Combustion. Fluorine can be burned in a flame employing hydrocarbon fuel under conditions such that fluorine provides some of the oxidation normally furnished by excess air. The products of reaction include hydrofluoric acid and carbon fluorides, the latter being inert gases with no odor. However, the hydrofluoric acid formed is objectionable and should be removed. Therefore, it is desirable, if any appreciable quantities of fluorine are to be vented, that the burner gases be scrubbed with water or alkaline solutions to remove the hydrofluoric acid. This presents an appreciable corrosion problem and equipment has to be constructed of carbon, lead, etc., to withstand dilute hydrofluoric acid solutions. This system has the disadvantages of requiring the combustion of some fuel at all times and is particularly disadvantageous for widely varying loads.Reaction with Water. The disposal of fluorine by water scrubbing is not satisfactory, because fluorine does not always react with water, for reasons unknown. Explosions have been encountered in such a system under some circumstances but not in others. Since there is insufficient information on how to control the reaction, it is not satisfactory for design at the present stage of development.Reaction with Carbon. The reaction of fluorine with carbon evolves so much heat that it is difficult to design safe equipment to handle such a process. Furthermore, the existence of an explosive compound FC (6) rules this method out.Absorption by Lime. The use of a lime slurry to remove fluorine in a liquid system is successful if sufficient contact time is provided. Because lime is a much more dilute alkali than caustic soda, the destruction of the intermediate compound, OF2, is more difficult than in the case of caustic soda. Insufficient experience has been accumulated to establish a satisfactory quantitative basis for design. Furthermore, difficulties attending the handling of slurries are involved.Absorption by Fluorides of Lower Valence. When inorganic fluorides, such as silver, antimony, cobalt, etc., are treated in their lower valence state with fluorine, they are oxidized to the higher valence state and the fluorine is absorbed. The compound of higher valence can then be reduced to its lower state by hydrogen, and the hydrofluoric acid formed can be condensed out in a refrigerated trap. This method is decidedly unsatisfactory for small installations and, for large installations, has the usual hazards of handling hydrogen as well as involving a series of operations.From the foregoing examples, it is clear that disposal of fluorine varies with the conditions involved, but the use of caustic, or of the salt-soda lime combination, represents the most convenient method for many installations.•

Corrosion Resistance of Platinum, Copper Nickel, and Tantalum in Liquid Oxygen Difluoride

“…Oxygen difluoride (99.5+% purity) was purchased from Allied Chemical Company and was purified by passing the vapor through a column of NaF pellets to remove traces of I-IF down to 0.02 v/o HF as an acid fluoride. NaF-HF (5). CO2 (max.…”

Pilot plant study of fluorine and its derivatives

“…The gas must not be vented to the atmosphere. The most convenient way of disposing of this gas is to burn it in the presence of city gas (natural or producer) and to absorb the hydrogen fluoride which is formed in an alkali solution (16). In these operations, the waste gases that contained fluorine were piped to a specially designed nozzle located at the center of a ring burner supplied with city gas.…”

Halogenation

“…Methods for disposal of waste fluorine vary. Scrubbing exhaust gases with caustic or soda-lime or burning a hydro-carbon such as propane with fluorine has been found to be applicable (196). Other developments in the industrial handling of fluorine are summarized by Landau and Rosen (111).…”