The use of ash from the incineration of sewage sludge for the production of high-phosphorus pig iron

Due to the current discussion about the use of sewage sludge in farming, the incineration of such slurries will be playing an increasingly important role in the next few years. Considering the shortage of phosphorus that is forecast for the next few decades, the question as to how phosphorus can be recycled into a reusable material in an environmentally friendly way should be given some thought. In the test described in this article 100-150 t ash from the incineration of sewage sludge were processed into high-phosphorus sinter, together with other phosphorus-bearing substances from residual materials. This sinter was then processed into high-phosphorus pig iron. The results have shown that ash from the incineration of sewage sludge can be used without problem in the production of high-phosphorus sinter material. In this process iron, silicon and phosphorus oxides are recovered, and environmentally relevant trace elements can be dissolved as trace elements (e.g. Cu, Cr, Ni) in the sinter for the production of pig iron, with quite positive effects on the properties of grey cast iron.