METHOD OF REDUCING SILICA AND ALUMINA FROM VOLATLE COAL ASH Russian patent published in 2010 - IPC C01B33/12 C01B33/32 C01F7/02 C04B7/26 C01B33/00 C01F7/00 

FIELD: chemistry.

SUBSTANCE: invention can be used to recycle volatile coal ash. Si is leached from volatile ash using NaOH solution with concentration of 40 wt % at 70-150 °C to obtain Na₂SiO₃. After leaching the Na₂SiO₃ solution and residue in which the ratio of Al to Si is greater than or equal to 2 are separated. Silica is obtained through carboxylation of the separated Na₂SiO₃ solution. CaO is added to the residue in ratio of CaO to SiO₂ less than or equal to 2, and alkali is also added to the residue in ratio of Na₂O to Al₂O₃ and Fe₂O₃ greater than or equal to 1-1.1. Suspended material is burnt at 950-1350°C to obtain slag which is dissolved in a diluted alkaline solution and the solid precipitate is separated from the liquid. The obtained liquid is carboxylated with precipitation of aluminium hydroxide which is then burnt to Al₂O₃.

EFFECT: invention enables highly efficient recycling of volatile ash.

5 cl, 7 ex