of fibre loss as well as reduced potential for plugging.

Results from the first installation After extensive internal testing in Andritz’s stock preparation pilot plant, the first commercial installation of a PrimeScreen X50

was as a primary coarse screen in a 1,350 bdmt/d OCC line. The main targets of the

installation were to: • Improve quality • Minimise energy consumption • Achieve longer screen basket lifetime

The PrimeScreen X50 was

installed in parallel with an existing conventional screen from another supplier and began operating at full production

immediately, using the same rotor tip speed, flows and consistency settings that were in place for the existing screen. The rated capacity of the X50 was 705 bdmt/d. First samples from the PrimeScreen X compared to the competitor’s unit are shown in Table 1. The competitor’s screen that

was replaced had 250 kW of installed power and operated at around 69 per cent load, as shown in Table 2. The PrimeScreen X had 132 kW installed power and operated at

Pulp Paper & Logistics

around 78 per cent load. This reduced energy consumption by 40 per cent (from 173 to 103 kW) compared to the existing competitor’s screen. The screen rotor in the PrimeScreen X was an LRs design, the screen basket an Rejector type (0.6 mm slot), that had 21 per cent less open area than the Rejector basket in the existing conventional screen. Even with this constraint, the PrimeScreen X operated with 5.5 per cent higher capacity and much better screening efficiency – especially for stickies removal with 77.5 per cent stickies reduction with the PrimeScreen X compared with the 56.4 per cent of the existing screen. Comparative data for the two screens is shown in Table 3. For this mill’s coarse screening

process, the average screen basket life in the existing screen was six-to-eight months. When the PrimeScreen X was opened up for inspection during a shutdown 10 months after installation, Andritz reports that the slot widths and profiles were excellent, and also that the underside of the rotor was exceptionally clean. Since that initial inspection, the mill continued to run the screen basket in the PrimeScreen X for 22 months before changing it. The PrimeScreen X is the natural

evolution of the ModuScreen pressure screen family. The targets for this development were to improve both the energy and screening efficiency, while making the unit easier to maintain. Andritz says it is suitable for all screening applications – brown and white grades, recycled or virgin, including coarse, fine, broke, thick stock, and fractionation duties.

Clamped screen basket design November/December 2019

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