ANDRITZ has successfully started up the latest innovation in dewatering – the Vertical Screw Thickener (VST) – at Zellstoff Pöls AG, Austria. The VST has been operating successfully since the beginning of December 2018 and supplying the existing MG paper production line PM2 with the maximum capacity of 360 t/d.
The pioneering Vertical Screw Thickener is a screw press with a vertical configuration and a very small footprint, making it suitable for retrofit installations in existing buildings. The pulp suspension is fed into the top of the machine, and its downward transport is gravity-assisted. At Zellstoff Pöls, the VST is located just before the finished pulp storage tank that feeds the paper production line and thus enables separation of the pulp mill and paper machine water loops.
The VST dewaters the pulp suspension from 3% inlet to 25-30% outlet consistency, and the water removed is recycled and re-used in the pulp mill. The ability to dewater from low-consistency inlet to high-consistency discharge is an important advantage compared to conventional dewatering equipment: Paper machine water is added to the dilution conveyor after the VST. Separation of the water loops results in savings in paper additives (e.g. sizing agent) at the paper machine. The VST replaces an existing gravity table at Zellstoff Pöls and feeds the MG paper production line for PM2.
Jürgen Rieger, Chief Operations Manager at Zellstoff Pöls, points out: “Our expectations of the new Vertical Screw Thickener were more than fulfilled. After the fast and trouble-free start-up, we are now already seeing the positive effects, like reduction of sizing agent consumption.” Patrick Wohlmuth, Process Technology Manager at Zellstoff Pöls, continues: “The results of our previous tests in the ANDRITZ Stock Preparation Pilot Plant were perfectly implemented in our mill-site production process with the VST 1005.”