Method for preparing fluoroboric acid from phosphoric acid by-product fluosilicic acid by wet method

The invention relates to method for preparing fluoboric acid by using wet-process phosphoric acid by-product hydrofluosilicic acid and a chemical production method, in particular to a method for preparing fluoboric acid by using wet-process phosphoric acid by-product hydrofluosilicic acid. The method takes the wet-process phosphoric acid by-product hydrofluosilicic acid and boric acid as raw material and comprises the steps: a. the hydrofluosilicic acid is put into a reactor to be preheated to the temperature of 40-45 DEG C; b. solid boric acid is slowly added into the hydrofluosilicic acid, the ratio between the actual dosage and the theoretical dosage of the boric acid is 0.95-1.05, and the feeding time is 20-30min; c. the reaction is carried out for 2-3h at the temperature of 60-70 DEG C; d. when the reaction stops, feed slurry is filtered, the filtrate is concentrated, filter mass is washed by distilled water, and washing liquid is used for circulating washing; e. the filtrate is concentrated to be more t