April 2008
By Justin Toland
After a tricky startup at its first mill in Burg, eastern Germany, Propapier has overcome the problems affecting PM 1 to such an extent that the unit recently set a new 24-hour speed record. On January 9, 2008, PM 1 ran at 1,366 m/min with 100 g/m2 fluting.
"We have seen a 90,000 tonne/yr increase in output in the last four years," notes production manager, Peter Resvanis. "There were more than 100 sheet breaks/month when I started (in 2004). There are 30/month now," he adds proudly.
Resvanis puts the improvements down to the hard work of the mill and its suppliers, chief among them Metso Paper, which delivered PM 1, the slitter/rewinder and various automation packages back in 2001.
A number of modifications have been made to the original design to get PM 1 up to speed and beyond. 'The first step was very important," says Resvanis, "The installation of a Lobemix system and some other modifications to stabilize the wet end."
Improving belt lifetime and dryness after the press section were other important tasks. The installation of a HiRun 2000 in the pre-dryer helped reduce draw, thereby improving stability, notes the production manager.
Changes to the sizer gave PM 1 another "big advantage" believes Resvanis. "The modifications cost a lot of money – around Euro 10 million ($15.2 million) - but 90,000 tonnes in four years is also a lot of money," he points out.
A closed loop process
Propapier Burg is one of the few mills in the world to have 100% closed water circulation – none is discharged, although the mill adds fresh water now and again to keep the level topped up. COD is 42,000 mg/L.
"The closed water loop has been very successful in the last four years," says Resvanis. To keep the machine clean, PM 1 is shut down once a week for about four hours and restarted at the lowest basis weight (100 g/m2).
PM 1 is fed with 100% recovered fiber (RCF): B12 and B19 mixed wastepaper, mainly sourced from the Berlin area, and W41 box edges, mostly from the Progroup's own box plants (see sidebar). Deliveries are in the hands of Progroup unit, Prologistik.
There is one infeed line for bales, leading into a Voith Fiber Systems stock preparation system (capacity: 1,180 tonnes/day).
The TwinDrum system, one of the first of its kind, starts working at a very high consistency (22-24%) in the first drum. The fiber is diluted to 4% consistency in the second drum before passing through a protector system (removing stones, sand, glass, etc) to coarse screening. The mill aims to keep a very low level of stickies, in order to avoid sheet breaks and maintain good runnability. At the same time, it is aiming to keep fiber losses below 1%.
The fiber is split into long and short fiber fractions and the two are treated separately. The short fibers go through four-stage cleaning (in cascade mode), while the long fibers go through both three-stage cascade mode cleaning and then three stages of lot screens in forward mode.
Propapier has an agreement with the energy company Kuhl, which takes away the rejects and burns them in a refuse-derived fuel (RDF) power plant.
The machine up close
At the headbox, PM 1 has two gap formers, with four wires in the wire section. There are two forming shoes, each with two vacuum chambers. The long fibers are on the bottom of the gap former but mainly form the top-ply of the paper (because of their strength properties). The bottom-ply mainly consists of short fibers and broke. The sheet consists of 30-40% long fibers and 60-70% short fibers. There is a couch roll for joining the two plies. Since each ply is about 50 g/m2 (a similar basis weight to newsprint), conditions at the wire section have to be very good to achieve good production.
The three-nip press section features a suction press roll in the first and second nips with a central roll and shoe press for the third nip. A steam box after the first nip helps to reduce the viscosity of the water in the sheet.
The dryness level after the press section is 52% (up from 22% after the wire section). The dryer section – 51 cylinders in total – is split into pre- and after-dryer sections, with an OptiSizer size press in between.
Starch is added to improve the strength of the paper and improve bonding between the two plies. Dryness at this stage is 68%.
The after-dryer starts with an AirTurn (to prevent sheet breaks). Following the seventh group, there are dryer cans in both upper and lower positions to prevent curling. Final dryness is 93%.
A Metso WinDrum slitter/rewinder (top speed: 2,700 m/min) splits the parent rolls into 2.5 m, 2.8 m or 3.3 m rolls for delivery to the Prowell box plants. The mill has fully automated vacuum roll storage.
A total of 115 people work at Propapier. In production, which operates on a four-shift system, there are two stock prep operators, three machine operators, two to three operators for the winder and starch sizer and one permanently stationed in the adjacent testing lab. There is an additional lab tester on hand during the day as well.
The lab features a Metso PaperLab unit for automated testing. The mill conducts key tests – CMT, SCT, Scott bond, burst – manually as well, "because these are the characteristics we have to guarantee," says Resvanis.
The production manager has been a papermaker 25 years, and appreciates the value of knowing the process beyond what is visible on a screen. "For the new generation of papermakers, it's a bit like Playstation 3. I have the mentality you have to know where your pumps are located."
Today, PM 1 is producing 320,000 tonnes/yr of testliner (100-180 g/m2, although the full window is 90-230 g/m2), an average of more than 3,000 tonnes/head/yr. "We are happy that the effort put in during the last four years has led to efficiency increases. It makes it fun to work here," says Resvanis. "We have very good cost development," he adds. "Some 20 euros/tonne maintenance costs and 8 euros/tonne wire costs."
New mill on the way
Lessons learned from PM 1 will be implemented during the startup of Propapier's second paper machine, to be located in a greenfield mill in Eisenhüttenstadt, some 10 km from the Germany's border with Poland, close to Frankfurt-am-Oder.
The 10-m wide, 650,000-tonne/yr Metso Paper PM 2 is set to start up in late 2009. "Progroup has to buy more than 400,000 tonnes/yr of paper from the market at the moment: the goal is to be independent from the market."
Progroup wants to be one of the top five in Europe for both containerboard production and converting. The new machine will produce fluting in a basis weight range of 70-130 g/m2 from B19 and B12 recycled fiber.
Some 20 employees from Burg will be transferred to the new mill. "Our whole strategy over the last four years has been to have everyone fully trained and qualified for the PM 2 startup," says Resvanis. Every quarter during that time, four Burg employees have been in school. "It has been difficult," admits Resvanis," but we found a good solution."
Burg mill manager, Götz Herold, explains that the new machine will be similar in many respects to PM 1, but with some exciting differences, including an OptiFlow headbox with dilution system, HiRun 4000 blow boxes, a TurnDry, and a WinDrum Pro X winder. Two years after startup. Herold would like to install an OptiDry Twin press section (initially PM 2 will feature an OptiPress). "I believe the OptiDry Twin is a revolution for recycled fibers," he says. "I'm sure that after two years we will need this system for the low basis weight grades for runnability," he adds.
Metso is delivering the stock preparation system to Eisenhüttenstadt in addition to the paper machine. The stock prep technology will be based around a low-consistency fractionation approach.
The new mill will be powered by an on-site RDF plant running on 350,000 tonnes/yr of rejects, including 80,000-90,000 tonnes/yr from the two Propapier facilities.
With paper from PM 1 and PM 2 primarily for internal use, customer satisfaction takes on an added level of importance. "Your 'mother' gives you what you need to live – you must be very careful what you send your 'mother'," says Resvanis.
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