The Ash2Salt process is built upon two preceding steps (as can be seen in the picture above). 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 sulfides 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.
LCA of our Ash2Salt process
It can be concluded from table 1 that the Ash2Salt process substantially reduces the impact of CO2-emissions on today's fly ash handling. It should be noted that the CO2 reduction of the Ash2Salt process heavy depends on the (reasonable) assumption that the salts recycled from fly ash replaces conventionally produced salts.
The LCA was carried out as a master thesis Kristin Johansson at Uppsala University and the Swedish University of Agricultural Sciences. The thesis can be found here (only in Swedish).