Methods for recovering fly ash using a selective flocculant

Abstract

Methods are described for treating fly ash sludge that includes calcium sulfate and/or calcium sulfite to selectively capture fly ash. The methods include treating the slurry with a first flocculant that selectively captures fly ash in the slurry relative to the calcium sulfate and/or calcium sulfite in the slurry, or alternatively selectively captures the calcium sulfate and/or calcium sulfite in the slurry relative to the fly ash, and clarifying the treated slurry to provide (i) a stream that includes relatively higher amounts of the calcium sulfate and/or calcium sulfate as compared to the slurry, and (ii) a stream that includes relatively higher amounts of the fly ash as compared to the slurry. Further processing of the stream that is enriched in fly ash can provide a high-purity fly ash product.

Dependencies are inferred from the claim text.