Ash2Salt

An unique process that recover clean commercial salts from fly ash

Summary of Ash2Salt

Background

Incineration is a common method for municipal solid waste treatment since it reduces the amount of waste, enables destruction of pathogens and organic contaminants, as well as possible recovery of energy in form of heat and/or electricity. Figure 1 visualize how fly ash is produced through incineration.

Even though incineration substantially reduces the waste’s volume and mass, bottom- and fly ash are produced in large quantities. The fly ash is captured in the incineration plant’s air pollution control and is often considered to be a hazardous waste when being disposed in a land fill. This is due to a high content of water-soluble chlorides and heavy metals in the fly ash. Because of its hazardous properties, it is expensive and problematic to manage.

Fly ash from Sweden is today mainly stored in special constructed land fills or on a discharged lime stone mine in Norway. The land fill and storing alternatives are not sustainable in a long-term perspective, but are temporary accepted because there is a lack of attractive alternatives.

Problem

The high chloride content of the ash makes it impossible (with current legislation) to land fill it without proper pre-management that avoids leaching of chlorides and stabilizes heavy metals. This pre-management is expensive and today only a few players can handle the fly ash. About 50% of Sweden’s produced fly ash is exported to Norway.

Solution

The Ash2Salt process is built upon two preceding steps. Fly ash is washed with water in the fist step and out goes washed ash (residual sand), and a leachate of salt and heavy metals continues to step two. In step two sulphides is used to precipitate heavy metals from the leachate and thereafter the chloride filled liquid continues to the Ash2Salt process in step three. In step three the Ash2Salt process takes place and CaCl2 (solution), NaCl, and KCl are produced with a single evaporator. In addition are extracted water from the Ash2salt process recirculated to the first step.

In a wash-plant for fly ash without the Ash2Salt process, following limitations exist:

  • The wash-plant must have permission to discharge large amounts of chloride effluents
  • The chlorine content of the ash can vary depending on what the incineration plants burn resulting in different amounts of chloride effluent must be discharged.
  • A need for fresh water

The main advantages of having the third Ash2Salt process step are:

  • Enables washing of fly ash without a discharge of chlorides
  • Can handle variations of chlorine content from the ash
  • Creates a source of income by production of pure commercial salts and ammonia
  • No need for fresh water since the Ash2Salt washes fly ash with land fill leachate and process water.

EasyMining’s patented Ash2Salt process is unique and can extract commercial salts from high chlorine containing fly ashes. After washing, the ash residue can be land filled without an exemption for high chloride contents. The Ash2Salt process can extract commercial grade:

  • Potassium chloride (KCl)
  • Sodium chloride (NaCl)
  • Calcium chloride (CaCl2)
  • Aqueous ammonia solution or ammonium sulfate