Fluorine Generation

Elemental fluorine is an important chemical in the nuclear industry for separation of uranium isotopes and also for the manufacture of SFg, fluorinated organics, and polymers. The only source of fluorine is electrolysis usually carried out in the eutectic KF 2HF at a temperature of 355-383K and using a current density of 70-200 mAcm [4, 17-19]. The selection of cell components and cell design is again determined by stability of materials to the very aggressive electrolysis 

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Fluorine was first produced commercially ca 50 years after its discovery. In the intervening period, fluorine chemistry was restricted to the development of various types of electrolytic cells on a laboratory scale. In World War 11, the demand for uranium hexafluoride [7783-81-5] UF, in the United States and United Kingdom, and chlorine trifluoride [7790-91 -2J, CIF, in Germany, led to the development of commercial fluorine-generating cells. The main use of fluorine in the 1990s is in the production of UF for the nuclear power industry (see Nuclearreactors). However, its use in the preparation of some specialty products and in the surface treatment of polymers is growing. 

Raw Material. The principal raw material for fluorine production is high purity anhydrous hydrofluoric acid. Each kilogram of fluorine generated requires ca 1.1 kg HE. Only a small portion of the hydrofluoric acid produced ia the United States is consumed ia fluorine production. The commercial grade is acceptable for use as received, provided water content is less than 0.02%. Typical specifications for hydrofluoric acid are... 

Potassium bifluoride, KE HE, is used as a raw material to charge the cells initially and for makeup when cells are rebuilt. A newly charged cell requires about 1400 kg KE HE. Overall consumption of KE HE per kilogram of fluorine generated is small. Gommercial-grade flake potassium bifluoride is acceptable. Its specifications are... 

To convert naturally occurring uranium oxide, yellow cake or U Og, to the gaseous UF, hydrofluoric acid is first used to convert the U Og to UF. Further fluorination using fluorine (generated from more HF) is employed to convert the UF to UF. The UF is then processed at gaseous diffusion enrichment plants. 

Figure 17.1 Schematic diagram of an electrolytic fluorine-generating cell.

Nickel can be used as an anode for fluorine generation, but losses due to electrolytic corrosion make it impractical for commercial production. 

Anode life, in laboratories, 536 Anodes, large, in fluorine generation, 542 Anodic dissolution and specific adsorption, 256... 

Bai and Conway discussion, 529 effect of polarization and fluorine generation on, 528... 

Emersed electrode, 12 Energy scales and electrode potentials, 7 Energy transitions via polaronic and bipolaronic levels, 362 Engineering models, for fluorine generation cells, 539 Esin and Markov plots, 259-260 Experimental data comparison thereof, 149 on potential of zero charge, 56... 

This volume contains six chapters and a cumulative index for numbers 1-33. The topics covered include the potential of zero charge nonequilibrium fluctuation in the corrosion process conducting polymers, electrochemistry, and biomimicking processes microwave (photo)-electrochemistry improvements in fluorine generation and electronically conducting polymer films. 

The reaction of nitrogen dioxide with fluorine generates nitiyl fluoride ... 

To decrease the risk of kilogram quantities of high-pressure fluorine on site of companies engaging in surface fluorination, on-site fluorine generation would be a very attractive alternative. This will decrease the amount of fluorine present on site at any given moment to a few kilograms with a maximum pressure of about 100 kPa. 

The process is characterised by the electrofluorination of volatile organic substrates within the matrix of pores of a carbon anode immersed in molten KF 2HF as electrolyte (as in a mid-temperature fluorine generator cell), and depends on the phenomenon that the anodically charged porous carbon is not wetted by the electrolyte. The fluorination probably takes place at the three phase interface of organic vapour, solid carbon, and liquid electrolyte in close proximity to, or at the sites where fluorine is being evolved. 

Figure 1. Flow scheme of a fluorine generator for fluorination...

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