Procédé et système pour extraire au moins une partie de la teneur en phosphore et/ou azote de boue et utilisation d'un système de distribution de suspension épaisse mobile sous la forme d'un récipient de cristallisation
A system and a method for extracting at least a part of the phosphorous content of a slurry, such as manure, wastewater and/or sludge, and recovering phosphorous and optionally nitrogen from the slurry by precipitating it as ammonium magnesium phosphate (NH4MgPO4) is disclosed. The method comprises transferring the slurry to a crystallisation container, adding a magnesium source, such as a magnesium salt, e.g. MgCl2, MgSO4 and/or magnesium oxide (MgO) and optionally an ammonium source, such as NH4Cl and/or NH4NO3 or anhydrous ammonia, in surplus in relation to the stoichiometric amount necessary for precipitating the phosphorous as ammonium magnesium phosphate (NH4MgPO4) to the crystallisation vessel and/or an inlet there-of. Then ammonium magnesium phosphate (NH4MgPO4) is precipitated on the inner surface of the vessel and/or as particles in the crystallisation container, and a phosphorous reduced slurry fraction is extracted. Struvite precipitate is recovered by extracting the precipitated ammonium magnesium phosphate from the crystallisation container by re-dissolving the precipitate in an acidic aqueous solution or by suspending precipitated struvite in an aqueous phase.
