Lödige ploughshare mixer conditions sewage sludge
A KM 300 DW ploughshare mixer from Lödige Maschinenbau is now used for conditioning in the new sewage sludge incinerator of the waste disposal company Zirngibl.
Zirngibl Verwertungs GmbH & Co. KG, based in Mallersdorf-Pfaffenberg in Lower Bavaria (Straubing district), is expanding its range of sewage sludge disposal services with a new mono-incineration plant with phosphorus recovery. To ensure an optimal thermal process, the sewage sludge must be conditioned there before incineration.
Precise pre-treatment in the ploughshare mixer
Mixing and structuring in a continuously operating KM 300 DW ploughshare mixer from Gebrüder Lödige Maschinenbau GmbH proved to be a suitable process for conditioning the sewage sludge accordingly. The model has a drum volume of 300 litres and is designed for a filling level of 50 percent. During the ongoing process, the mixer is continuously fed with moist and partially dried sewage sludge via an automated transport process.
The machine is based on the fluidised bed process introduced to industrial mixing technology by Lödige, which ensures very good mixing: Specially developed, ploughshare-shaped blades rotate close to the wall in a horizontal drum, creating a fluidised bed. In addition, the mixing tools in the current application have welded studs and additional wear protection on the edges and sides.
Sophisticated product in terms of process technology
The fluidised bed process enables a high degree of homogeneity with constant reproducibility and, last but not least, low mechanical energy input. It therefore offers good conditions for ensuring a pumpable consistency of the sewage sludge. This is because the material is quite demanding in terms of process technology: in the so-called glue phase, it is tough and almost dough-like.
For this reason, the use of a conventional mixing screw instead of a mixer was ruled out: Because the material tends to be ‘kneaded’ with this technology instead of a fluidised bed, the screw quickly becomes clogged. In the solution now realised, the moist sludge is instead added to the mixer, where it is mixed or ‘breaded’ with the dried sludge.
