METHOD FOR CREATION OF ESPECIALLY PURE GRIT OF CRISTOBALITE Russian patent published in 2019 - IPC C01B33/12 C03B1/00 

FIELD: technological processes.

SUBSTANCE: invention can be used in chemical and electronic industry. Purified grit of silica from high-purity quartz concentrate with total content of controlled elements – impurities at level of 10–20 ppm is loaded into quartz tubular container installed in heating furnace, poured with 20 % aqueous solution of ammonium chloride, heated to 80–90 °C. Grit is stirred by oscillation and rotation of container for 30 minutes, then solution is drained through polyamide sieve with cells of 0.09 mm. Remaining wet grits in container, while stirring, is heated to 120±10 °C and maintained at this temperature until its complete drying. Thereafter, the mixed grit is heated to 1,350±10 °C at rate of 25–30 degrees/min and irradiated with ultraviolet for atomisation and ionisation of molecules of chlorine and hydrogen formed due to sublimation of ammonium chloride from surface of grit grains. Grit is maintained at this temperature for 60 minutes, after which ultraviolet irradiation is switched off and the container is blown with special purity argon. Residues of sublimate of ammonium chloride dissociated with ultraviolet radiation and vapour-gas reaction products of grit impurities are removed through a bubbling water chamber into a ventilation system. Then the container is evacuated without oil pumping means to pressure 1×10⁴ Pa, is filled with high-purity oxygen, includes ultraviolet radiation for atomisation of oxygen molecules, heated to temperature of 1,350±10 °C and held at this temperature for 1 hour. At the end of the oxygen treatment cycle, the ultraviolet exciter is switched off, the container is stopped and blown with highly purified argon and the container is cooled to ambient temperature. After that, the purified and cristobalized grit are poured into a sealed container.

EFFECT: disclosed method is used in making especially pure grit cristobalite from powder of amorphous synthetic silicon dioxide and grit of quartz glass, simplifies cleaning technology, reduces harmful factors of refining process.

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