Aluminum fluoride

Aluminum trifluoride (AlF3) is the most in-demand fluorine-containing product (available in the form of crystalline powder). It is mainly used in the production of primary aluminum. In small quantities it is used in the manufacture of optical glasses, automotive engineering, construction, pharmaceuticals and other industries.


Aluminum fluoride powder

According to our technology, aluminum trifluoride is obtained during the processing of fluosilicic acid (H2SiF6), a by-product of wet-process phosphoric acid (WPA) production. This technology implements the principle of comprehensive processing of mineral raw materials, allows the production of high-quality products (AlF3, SiO2), meets BAT standards and is perfectly integrated into the production structure of the mineral fertilizer production plant.

By many years of work on improving the technology of aluminum fluoride from fluosilicic acid we achieved the following results:

  • high-quality products (minimal impurity content and excellent fluidity);
  • minimal raw material consumption;
  • high energy efficiency;
  • minimal emissions and no discharges.


Process flowsheet

1 - aluminum hydroxide bin; 2 - agitator; 3 – FSA storage; 4 - burner; 5 - belt vacuum filter; 6 - tank; 7 - crystallizer; 8 - bin; 9 - drying-calcination burner; 10 - cooler; 11 - tubular belt conveyor; 12 – fan; 13 – cyclone; 14 - bag filter; 15 - HFS.

Technology description

The key stage of the technology is neutralization of fluosilicic acid with aluminum hydrate and effective separation of the resulting slurry with washing of the hydrated SiO2 precipitate.

H2SiF6 (р) + Al(OH)3 (тв) → AlF3 (р)+SiO2·nH2O +Н2О

AlF3 solution crystallizes in the presence of seed. The resulting slurry is separated on a filter to obtain AlF3·3H2O wet crystals.

AlF3 (р) + 3Н2О → AlF3·3H2O (тв)

The mother liquor is used in WPA production or neutralized with obtaining of cooling water.

Very important is the stage of drying-calcination of aluminum fluoride trihydrate crystals. The process is complicated by the fact that at high temperature aluminum fluoride is susceptible to pyrohydrolysis. JSC NIUIF jointly with LLC Chemtechnology developed and implemented an innovative method of one-stage drying-calcination. This method allows to reduce the amount of necessary equipment and, in comparison with two-stage method, significantly reduce the resource consumption (electricity, fuel, water), and minimize emissions of harmful substances into the atmosphere.

Guaranteed raw material and energy specific consumption

Raw material and energy consumption (per ton of ph. m. of final product)

Fluorosilicic acid (H2SiF6)

1,23 t

Aluminium hydrate (in terms of Al2O3)

0,85 t

Heat (natural gas)

0,16 ton of reference fuel

Electricity (0.4 kV)

200 kWh

Steam (4-6 bar)

0,85 Gcal

Cooling water

10 m3

   Aluminum fluoride quality

Parameter

Guaranteed

Expected

Mass fraction of AlF3, not less than

96 %

97 %

Mass fraction of Al2O3, not more than

4 %

2 %

Mass fraction of SiO2, not more than

0,25 %

0,1 %

Mass fraction of Fe2O3, not more than

0,08 %

0,01

Loss by calcination, not more than

2,5

1

Mass fraction of more than 45 microns, not less than

90%

97 %

Angle of repose, not more than

33

32

Bulk density, not less than

700

750

Fluidity, not more than

120 sec

100 sec


In 2015, at JSC Apatit (Cherepovets), a revamp of the existing AlF3 production was completed. The achieved capacity amounted to 56 thousand tons of AlF3 per year.