Fluoride salt effects on the decomposition of dolomite

From DTA and isothermal studies, it is evident that the temperature of decomposition of dolomite is reduced and that the rate of decomposition is enhanced relative to pure dolomite when small amounts of fluoride salts, e.g., LiF, NaF, MgF₂ and CaF₂ are mixed with the dolomite powder. From X-ray analysis pure dolomite is seen to decompose directly into CaO and MgO but when the fluoride salts are present at 800 °C it initially decomposes into MgO and CaCO₃. The contracting area was used for describing the decomposition kinetics for each case. The reaction rate constants are much higher when LiF and NaF are present at 635-800 °C whereas only at 800 °C do MgF₂ and CaF₂ enhance the decomposition process. These differences were attributed to the higher vapor pressures and ease of transport for LiF and NaF. It is further suggested that lower temperature eutectics are formed between dolomite and its decomposition products and the fluoride salts which then affect the decomposition process.