CO2-neutral cement with 80% process water recovery
DEFINITIVE SOLUTIONHaving been positively surprised to receive a Circular Economy grant from the Municipality of Rotterdam, we launched the Process Water Recovery project. The major challenge lies in the fact that the AC Minerals process—which recovers high-quality cement from asbestos-cement roofing sheets and pipes—creates an alkaline phase within a slurry that requires large amounts of water. From a sustainability perspective, it is highly worthwhile to recover as much of this water as possible for reuse in the process. The dewatering technology employed recovers 45% of the filtrate in each cycle. In the current research project, this filtrate will be reused multiple times within the alkaline phase. This has led to the theoretical projection that the alkaline phase might require only 20% fresh water. For the new AC Minerals plant to be built in Rotterdam, this means that the annual fresh water requirement would be just 5,000 tonnes, rather than 25,000 tonnes.
Reuse of process water is only feasible if no substances precipitate in the filtrate that could interfere with the dewatering process or the process for destroying asbestos fibers and recovering high-quality reactive cement as a clinker substitute. This means that, to reach final conclusions for this project, the process steps following dewatering must also be carried out and analyzed: the drying process and the thermal treatment for the complete recrystallization of the asbestos fibers—a process already validated by DNV.
The final report on process water recovery is expected spring 2027.
