Washing of screenings and simultaneous dewatering with high pressure
Conventional high pressure units often achieve only poor dry substance contents (DS) when processing municipal screenings without prior washing. The viscosity of faeces, grease and sludge, which are always contained in the screenings, does not allow built-up of higher pressure in the press (see fig. 1). It is absolutely necessary therefore to have the screenings washed before in order to achieve high DS contents.
This conventional way of screenings treatment causes often very high investment, maintenance and spare parts costs. The new WAP high pressure wash press (WAP/HP) is a successful symbiosis between the well-proven high pressure component of the ROTAMAT® wash press type Ro4/HP and the WAP wash press. Screenings washing takes place in the wash zone, like in the WAP, which is located in the conveyor pipe. The washed screenings are then conveyed into the high pressure cone where intensive pressing takes place.
The intelligent technique in the high pressure cone allows to react within seconds to possibly occurring material changes in the screenings, i.e. the machine operates permanently at the highest pressure in the press zone and achieves therefore continuously excellent DS contents between 50 and 60%, as the first reference plants show!
By Wolfgang Branner, product manager