Stendal: Never standing still

Unless it’s a newly-built mill, it’s rare for a SPECTRUM article to cover diverse process areas from the woodyard to the recovery island to the fiberline. And yet, this article will do exactly that, because ANDRITZ is involved throughout Mercer International’s Stendal mill in Germany.

ANDRITZ is involved throughout Mercer International’s Stendal mill in Germany from the woodyard to the recovery island to the fiberline.

When Adolf Koppensteiner became Managing Director at Stendal in 2013, he immediately spearheaded a program to establish “world class” availability by 2018. He explains, “It is a continuous improvement program. A mill is never totally up to date. If you stand still, you go backwards.”

In 2014, Stendal set a new annual production record and reached a daily production record in 2015.  Koppensteiner describes the progress as “huge steps forward”.

ANDRITZ has been a technology and service provider for Stendal since the mill started up in 2004, delivering the major chemical recovery systems.  That relationship has continued, with ANDRITZ providing technical services, rebuilds, upgrades, and modernizations to keep the mill updated and efficient.

The ANDRITZ ScanChip analyzer monitors chip quality and helps the mill determine the optimum time for chipper knife changes. Josef Ertl, ANDRITZ Product Manager (right), pours chips into the analyzer as Steffan Ratzlow, Zellstoff Stendal’s Fiberline Manager, looks on.

Harald Fichtl, Zellstoff Stendal Production Manager

Upgrade in white liquor filtration

ANDRITZ also upgraded the CD filter in the white liquor plant, making it possible to use 12 discs instead of the current 10. The upgrade also moved the location of the suction head outside the unit. “This makes maintenance much easier and we don’t have to take downtime,” says Patrick Ludwig, Production Engineer at Stendal.

Raising boiler performance even higher

According to Jan Peter Daum, Stendal’s Recovery Manager, their recovery boiler is operating stably, with no fouling or plugging, and with the lowest residual oxygen content in the world for any boiler running at high load – 25 tds/d/m2 – without exceeding environmental regulations. In addition to delivering the boiler, ANDRITZ recently entered into a six-year contract with Stendal to improve performance without major upgrades.  As Daum puts it, “We want a long-term partnership so both sides have security and can set performance goals.”

Koppensteiner points out that while such a long-term contract may be unusual, “It is normal if you are satisfied with your partner, and if your partner can give you something extra. We are certain that we can still improve our relationship.”

To remove bottlenecks and upgrade the evaporation plant, ANDRITZ delivered new equipment on a tight deadline. The 20% increase in evaporation capacity also allows the recovery boiler to burn higher solids black liquor.

Knife skills

Starting in the woodyard, ANDRITZ has been busy rolling out its PartnerChip concept from ANDRITZ Iggesund Tools, which combines a knife replacement program (TurnKnife system) and a ScanChip analyzer to improve the chipping operation.  Steffan Ratzlow, Stendal’s Fiberline Manager, says, “We used to have problems with chip homogeneity and knife changes were difficult and risky for us.”

Continuous thinking about batch

To help improve the availability and productivity of Stendal’s 10 batch digesters, ANDRITZ felt that Stendal would benefit from a tailored version of the Diagonal Screen that is so popular in continuous digesters.  Walter Scholz-Sommerbauer, ANDRITZ Key Account Manager for Stendal, explains, “Our design, tailored for their batch digesters, is minimizing production losses and reducing downtime.”


Wash press renewal

Stendal wanted a pair of new rolls for their wash press to replace the older ones.  Instead of contacting the OEM, they asked ANDRITZ to take a look at the surface damage on the old rolls caused by mechanical characteristics of the press. Harald Fichtl, Production Manager, says that Stendal knew ANDRITZ had experience with technology to achieve durable and long-lasting rolls.

Evaporation “win-win”

ANDRITZ’s biggest upgrade project so far has been the expansion of the mill’s evaporation plant. According to Tapio Lintunen, Senior Project Manager for ANDRITZ, the technical challenge was to reconfigure the system – which was operating significantly above design capacity. Fichtl explains, "The old plant was a bottleneck, even though we were running at 120% of design capacity.”

A challenging part of the project was the timing. Not only was the delivery deadline tight, the start-up had to occur during two short shutdowns.  “All of the tie-ins to existing equipment had to be completed during the two-day shut in October,” Lintunen says.  In addition to eliminating the bottleneck, the recovery boiler can now burn higher solids. A 20% increase in evaporation capacity also means reuse of more condensate and less COD into the river.


This way, it is a win-win situation that rewards both partners for improvements."


Managing Director, Zellstoff Stendal


Both the equipment and the team were right”


Technical Manager at Zellstoff Stendal

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Walter Scholz-Sommerbauer
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