Method for removing impurities from an alkali metal chlorate process

Abstract

The invention relates to a method for removing calcium ions and silicon compounds from various liquors produced or obtained in an alkali metal chlorate process, thereby reducing the operating cost and improving the possibility to close the process further. The calcium ions and silicon compounds are removed by addition of carbonate ions for precipitating calcium carbonate and by addition of an iron-containing compound for forming and precipitating a complex of iron ions and a silicon compound, whereupon the precipitates are co-separated from the liquor. The removal of calcium and silicate ions is substantially facilitated by the simultaneous separation of the precipitates. Subsequently, the excess of carbonate ions can be reduced by acidifying the electrolyte for releasing carbon dioxide.

Dependencies are inferred from the claim text.