Production process of magnesium fluosilicate

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1.1 Experimental Materials and Principles Fluorosilicic acid with a mass fraction of 12%~22% and industrial light magnesium oxide (HG/T 2573—2012) are used as raw materials. The main components of industrial light magnesium oxide and their respective mass fractions are: MgO, 92%~95% ； CaO, 0.5%~2.0% ； Sulfates, 0.2%~1.0%. Main reactions in the synthesis process: MgO + H2SiF6 = MgSiF6 + H2O; CaO + H2SiF6 = CaSiF6 + H2O; MgO + 2HCl = MgCl2 + H2O. 1.2 Experimental equipment: A synthesis tank lined with rubber, with a volume of 21 m3 ； Plate and frame filter press ； Vacuum concentration evaporator ； MSMPR cooling crystallization tank ； Centrifuge ； Dryers, etc. 1.3 Experimental process and procedure The main steps of the process are as follows: 1) The operation sequence of adding acid first and then the MgO powder suspension is followed: H2SiF6 is added to the synthesis tank, where the temperature is maintained at 50 ℃ with continuous stirring; thereafter, the magnesium oxide powder suspension is added to it, with the reaction time controlled at 1 hour [3–4] ； 2) The reaction product is filtered by pressure filtration; the filtrate is evaporated and concentrated to the desired concentration. Cooling and crystallization yield a slurry containing magnesium fluosilicate crystals, which are then cooled, spun to remove excess liquid, and the resulting crystalline product is rapidly dried in a stream drying tube ； 3) Adopt the procedure of adding MgO powder first and then acid: First, add warm water at 50 ℃ to the synthesis tank, and start the screw feeder to add the pre-calculated amount of magnesium oxide powder to it. Then, add H2SiF6 with different mass fractions (12%, 16%, and 22%) to it, controlling the reaction time at 1 hour ； Repeat the steps in 2) above.