Process & contact
AshDec (Metso Outotec)
Member of ESPP
Updated 1/2024
Input materials
All ashes with P-content >7%
Output products
Modified Rhenania Phosphate (Calcium-Sodium-Phosphate) Pnac solubility >80%; granular material with P2O5 content of 15-25% (depending on input-ash); no organic matter; product is blendable with all other fertilising products.
Process description
Ash is mixed with a sodium carrier (Na2CO3 or NaHCO3) and heated to about 850-900°C in a rotary kiln to modify the P-compounds to neutral-ammonium-citrate soluble CaNaPO4 (Rhenania Phosphate). Heavy metals are partly removed and captured in a baghouse filter from where they can be separated from the fertilising product as a small waste stream (3-5% of input material). Hence, > 97 % of phosphorus and other elements in input ash are recovered.
Recovery rate (P in final product / P in input ash): >95 %
Recovery rate (% from input ash in recycle stream) of iron, aluminium: >95%.
Removal of heavy metals (% from input ash in final phosphate product): Cd: ~ 50 % removal, Pb: ~10 %, As: ~ 50 %.
Cu, Zn and Ni are not removed from the ash with the standard process. Removal of Cu and Zn can be enhanced by use of chlorine additives.
Operating status
Pilot plant (300 kg/h, photo) operational for several years, Leoben, Austria. Continuous operating campaigns produced several hundred tons of product.
A full scale plant (30 000 t/y ash input) is planned in Altenstadt (Bavaria), with Enter GmbH and sePura GmbH, in the R-Rhenalia RePhoR project. This uses as input 55 kt/y of sludge (as DM) and will produce 15 kt/y of ash, which contains 1.5 kt/y P. The incineration and AshDec sections will be integrated.