Cyclic preparation method for producing titanium boride from intermediate feedstock sodium-based titanium-boron-fluorine salt mixture and producing sodium cryolite as byproduct

A cyclic preparation method for producing titanium boride from intermediate feedstock sodium-based titanium-boron-fluorine salt mixture and producing sodium cryolite as byproduct, wherein the method comprises the following steps:

• A) boric acid or boric anhydride is added with hydrofluoric acid to generate fluoroboric acid by reaction at 100-200° C., the fluoroboric acid is then added with sodium carbonate aqueous solution for reaction to generate sodium fluoborate solution, and the sodium fluoborate solution is concentrated, crystallized and bleached to obtain sodium fluoborate;
• titanium-iron concentrate is added with hydrofluoric acid to generate fluotitanic acid by reaction at 100-200° C.;
• the fluotitanic acid is then added with the mixed salt aqueous solution of sodium carbonate and sodium hydroxide, pH is controlled within a range from 3 to 4, and after water and oxides of ferrous iron and ferric iron are separated, the mixed salt aqueous solution is further added to result in pH within a range from 7 to 8 so as to obtain sodium fluotitanate solution, and the sodium fluotitanate solution is concentrated, crystallized and bleached to obtain sodium fluotitanate;
• B) the sodium fluoborate and the sodium fluotitanate are put in a reactor based on a molar ratio of 2:1, inert gas is fed into the reactor after evacuation, the reactor is heated up to 700-800° C. and then added with aluminum, and titanium boride and sodium cryolite are generated by rapid stirring and then reaction for 4-6 hours;
• or aluminum is put in the reactor, inert gas is fed into the reactor after evacuation, the reactor is heated up to 700-800° C. and then added with the sodium-based titanium-boron-fluorine salt mixture of sodium fluoborate and sodium fluotitanate based on a molar ratio of 2:1, and titanium boride and sodium cryolite are generated by rapid stirring and then reaction for 4-6 hours;
• C) the sodium cryolite is sucked out and then fed into a rotary reaction kettle together with concentrated sulfuric acid, hydrogen fluoride gas as well as sodium sulfate and sodium aluminum sulfate are generated by reaction in the rotary reaction kettle, and the hydrogen fluoride gas is collected and then dissolved in water to obtain hydrofluoric acid;
• the solid mixture of sodium sulfate and sodium aluminum sulfate is crushed and then dissolved in water, sodium hydroxide is added for the purpose of reaction, and sodium sulfate aqueous solution is obtained after solid aluminum hydroxide is separated;
• and
• D) the obtained hydrofluoric acid aqueous solution is recycled either for leaching titanium-iron concentrate to prepare sodium fluotitanate, or for leaching boric acid or boric anhydride to prepare sodium fluoborate.