“We got exactly what we wanted.”

New screw, new performance

After around 20 years of operation, Pfleiderer wanted to resolve some operating pressure issues, and get the plant ready to meet to the industry’s next-generation challenges. This included replacing the digester discharger with a new unit that better matched their mechanical, quality and profitability goals. They asked ANDRITZ for a tailor-made discharger, with the exact proportions that would enable Baruth to operate at the “sweet spot”. As Alexander Held, Technical Services Director, Pfleiderer, explains: “We wanted a new, state-of-the-art digester base unit, designed with diameter and pressure levels to fit our requirements.”

The upgrade required quite a few innovations, and ANDRITZ was glad to contribute. Alexander Held remarks, “We’ve never had a partner before that was so open to non-standard requirements; ANDRITZ really listened and immediately understood our wishes.” Karl Rausseck, Technical Services, Pfleiderer, adds, “The experience from planning phase to final design was very positive - unique. I’ve never seen such a good design.” Florian Grünberger, ANDRITZ Key Account Manager, admits, “Our customers usually run their refining systems for decades. Over such long periods, production capacity, fiber quality and energy consumption requirements can often change. It was great to be able to offer a tailor-made solution for a customer with specific requirements, to adapt to changing production conditions.”

The newly-designed digester discharger works quite differently from the old one. Instead of being a classic drop feeder, the new unit compresses the cooked woodchips via a slightly conical screw set-up, to create chip plugs. These then enter the new ANDRITZ C-Feeder (constant feeder), which slices the chip plugs into small, equal-sized pieces, to ensure a highly-consistent feed volume entering the refiner. Other innovations included a central steam unit, which gives Pfleiderer the option of a third steaming stage, especially for any fiber clumps that may have evaded the two steaming stages inside the digester itself. This helps to ensure less-variable temperatures, and that can actually reduce overall steam consumption. “We have been using this option since Day 1, right from the startup”, explains Alexander Held, while Christoph Liese, Production Manager, Pfleiderer, confirms, “We have a good steam spread now.”

A further innovation was a new wear ring inside the digester base, next to the agitator tips. ANDRITZ also provided a cartridge solution for the bushing of the agitator shaft. This can be swapped out at planned service intervals, saving time and money on changeovers, which are now seven times faster. Karl Rausseck adds, “We made many practical changes, to simplify the system. For example, we rotated the agitator drive by 90°, to make it more easily accessible. It was a really good decision; it makes it much easier to install spare parts, reducing costs and downtime.”

Need for feed

A new, compact and maintenance-friendly C-Feeder was also manufactured to Pfleiderer’s specific design. This state-of-the-art unit replaced the old twin-screw design with a single screw. Karl Rausseck explains: “I was skeptical, at first. I’ve been working on this digester for more than 20 years, and I was afraid the C-Feeder wouldn’t be able to handle the operating conditions: there can be some big fiber chunks to deal with. But it has turned out to be really solid.” Florian Grünberger understands: “It’s a more complex piece of equipment, so Karl was afraid it would be more sensitive, but in fact, it is very robust.”

The new C-Feeder works together with the new digester discharger to ensure continuous feeding of wood from the base of the digester into the ribbon-feeder, to match the new throughput capacity needs. This means it now operates with far more consistent energy consumption, which reduces operating expenses and extends refiner plate lifetimes (assuming like-for-like fiber characteristics). Another major advantage is homogeneous defibration, which means the plant uses a lot less adhesive during production, while delivering reliable board properties in all capacity ranges. We believe Pfleiderer Baruth may now have the most advanced refiner-feeding system in the industry.

All targets hit

The new equipment arrived at Pfleiderer Baruth in September 2023, and the upgraded system started up in October, on time, as planned, with no delays. David Klement, ANDRITZ Project Manager, notes, “The project installation took place during three weeks of downtime, exactly as planned. There were some obstacles – there always are – but we trusted our design, combining the old and the new equipment, and it worked. Pfleiderer noticed an improvement right from the startup - they can ‘hear’ that it is running quieter now.” Christoph Liese confirms, “There were no installation problems, no major issues with the startup. And there have been no stoppages since, no trouble with worn parts – it’s working well and running smoothly. We hit all of our targets. There has been a clear improvement in all variables. The project was a success and we would absolutely recommend this system.” Alexander Held concludes, “It was almost a ‘plug-and-play’ solution. We were already achieving our savings targets as early as January 2024,” (just three months after startup). “From our side, this is a real success story. We got exactly what we wanted.”

According to Christoph Schwarz, ANDRITZ Product Manager, “Pfleiderer is a very careful customer, keeping a keen eye out for any difficulties. So from such a high-precision customer, this is very high praise, indeed.”