Production of synthetic cryolite by wet-process phosphoric acid defluorination
The mass ratio of fluorine in phosphate rock is 2％-3％,when sulfuric acid is used to leach phosphate rock into wet-process phosphoric acid,fluorine will enter the liquid phase,resulting in a high fluorine content in the wet-process phosphoric acid,which is not conducive to the subsequent refining,can also damage equipment,affect production and cause economic losses.Fluorine is a kind of scarce resource,simultaneously recovering and utilizing fluorine in wet-process phosphoric acid can achieve resource recycling,reduce production costs and minimize pollution.By adding sodium fluoride and hydrofluoric acid to decolorized wet-process phosphoric acid,synthetic cryolite is prepared while removing fluoride.The effects of sodium fluoride and hydrofluoric acid dosage,reaction temperature,reaction time,addition method of sodium fluoride and droplet rate of hydrofluoric acid on the molecular ratio of synthetic cryolite are studied.The results show that,when the mass of decolorized wet-process phosphoric acid is 400 g,the total amount of sodium fluoride is 28 g,which is added twice,the total amount of hydrofluoric acid is 13 g,and the droplet rate is 1.6 mL/min,the reaction temperature is 60 ℃,the reaction time is 1 h,the molecular ratio of synthetic cryolite produced by defluorination is as high as 2.92,meeting the requirements of synthetic cryolite with high molecular ratio of CH-1 in GB/T 4291-2017.
wet-process phosphoric acidrefiningdefluorinationsynthetic cryolite with high molecular ratio
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