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Montanuniversitaet launches 4.5 million euro EU-project for recovering phosphorus from sewage slduge Print
Phosphorus is vital for the human and animal health, just consider for instance that the human body contains up to 0.75 kg of phosphorus. Natural phosphate sources low in heavy metals however are getting scarce worldwide. Thus, for many years new ways have been examined on how to recover phosphorous from sewage sludge. From these research activities, two main procedures have evolved: the wet-chemical and the thermo-chemical approach, however none has yet been realised in industrial scale.

"Recovering phosphorus has been a great challenge so far", Prof. Harald Raupenstrauch, Chair of Thermal Processing at the Montanuniversitaet Leoben, explained. "Therefore, we have submitted an EU-funded research project dealing with the recovery of phosphorus from sewage sludge and sewage sludge ashes with the so-called RecoPhos-Process. We have been awarded 4.5 million euro for the project and will be coordinating all the research activities for the next three years", Raupenstrauch said.

Project partners are the University of Stuttgart (Germany), SGL Carbon GmbH (Germany), M.A.L. G.m.b.H. (Austria), INERCO S.A. (Spain), InsPyro N.V. (Belgium), Hariri Chemical Process Engineering (Switzerland), Jeloga Engineering (France), M.I.T. – Metallurgy & Inorganic Technology (Austria), and GCTU GmbH (Germany).

With the new RecoPhos-Process, phosphours of the highest quality can be recovered from sewage sludge and its ashes, as well as other sources such as meat and bone meal, due to a reaction mechanism similiar to the Woehler-Process. Unlike in the typical process, where the use of sludge ashes is limited because of their high iron content, in RecoPhos the reduction of phosphates takes place in a thin film on the surface of the inductively heated coke bed of the novel "InduCarb" reactor. Coke or alternative materials act as reducing agent; the flux SiO2 is contained in the ash. The reduced phosphorus can evaporate from the film without significantly reacting with other elements present in the melt, making the use of all kinds of sludge ash possible. Other output materials will be a metal alloy and a silicate slag, as well as a high-energy gas.

Another difficult task in P-recovery from sewage sludge is the separation of heavy metals from the other products. The heat required for the melting can be obtained by the addition of dried sewage sludge to the process.

Further information:
Univ. Prof. Harald Raupenstrauch
Tel.: +43 3842 402 5800
E-Mail: harald.raupenstrauch@unileoben.ac.at

Representatives of all project partners with Rector Eichlseder (left) and Prof. Raupentrauch (right, first row).