When flue gases are purified during waste incineration, fly ash is generated - a hazardous waste with high levels of heavy metals and chlorides. In the Ash2Salt process, the fly ash is washed, and three commercial salts are extracted from the wash liquid: sodium chloride, potassium chloride, and calcium chloride.
The process is preceded by two pre-treatment steps. In the first step, fly ash is washed with water resulting in a cleaned ash and a leachate containing mainly chloride salts and heavy metals that continues to the second step.
In the second step, sulphides are used to precipitate heavy metals from the leachate and the resulting chloride-saturated liquid then continues to the Ash2Salt process.
The Ash2Salt process separates calcium chloride (CaCl2), potassium chloride (KCl) and sodium chloride (NaCl) by the use of a single evaporator. In addition, water extracted from the evaporator is recirculated to the initial washing step.