I.J. van der Walt

The beneficiation of CaF 2 to produce fluorocarbons and hf by means of hightemperature plasma processes

Fluorspar (CaF2) is the most important source for the manufacturing of F-compounds, e.g. HF and F2, and derived products like fluorocarbons. South Africa has the second largest reserve base of fluorspar in the world, and is the third largest global supplier. However, it exports the bulk of its fluorspar unbeneficiated and only about 5 % is beneficiated locally, mainly at Necsa for the production of HF, via the conventional sulphuric acid digestion process. Hightemperature plasma processes offer a unique method to access the F-values contained in CaF2.

A thermal non-transfer arc V-type torch plasma

Conventional linear DC plasma torches are known to have a relative long tail flame wherein a high temperature chemical reaction can be performed or where the plasma can act as a heat transfer medium. Introducing solid particles into these plasma torches generally destabilizes the plasma and may cause extensive erosion on the anode, thus shortening the torch operational time significantly. In this torch the solid particles are exposed to the arc temperature and not only the tail flame temperature. This torch enables one to introduce solid particles in very close proximity of the plasma arc and if the particle velocity is optimized, the particles may even penetrate the arc. This paper presents the design and typical operating parameters of a V-type plasma system, and discuses the advantages and disadvantages of such a system.