Aluminium fluoride and/or cryolite prodn - from silica-contg fluorspar and sulphuric acid with direct heating of the mixture

摘要

Fluorspar, which may contain a large amt. of silica, is mixed with H2SO4 and heated directly in a rotary kiln with combustion gases, which may contain water vapour; and the resulting mixture of H2SiF6 with varying amts. of HF is absorbed in water and converted to AlF3 and/or cryolite. Thus, inexpensive, silica-contg. fluorspar can be utilised without any enrichment.