Graeme Rodden, Editor, Pulp & Paper magazine, RISI
March 1, 2004
Like a sentinel on duty, Sappi's Lanaken (Belgium) mill is prepared, as mill director Jos Pijls says, "To fulfil our role in the Sappi family."
The readiness comes about through a number of projects that have culminated in the development of a new paper grade, Royal Xpress.
The most recent project was the addition of a new refiner, bringing the mill's BCTMP capacity up to 180,000 tonnes/yr. Lanaken laid claim to the title of world's first integrated CTMP mill (Lanaken uses the CTMP designation for its standard spruce: poplar pulp; BCTMP for 100% poplar pulp) when Phase I of its mechanical pulping plant started up in 1987. Phase II began in 1989 while Pijls considers the latest project Phase III.
The mill uses a combination of spruce and/or poplar. As making poplar pulp needs more power, capacity when the mill is running a poplar campaign is 140,000 tonnes/yr. In tonnes/day, Lanaken can now make 509 tonnes of standard BCTMP, up from 382 tonnes, or 382 tonnes of poplar BCTMP, up from 286 tonnes. Hydrogen peroxide is the bleaching agent used. Pijls explains that if Lanaken produces more Royal Xpress paper, then it needs more poplar pulp, thus reducing the capacity of the BCTMP mill. Therefore, the mill added the new refiner, a Metso RGP 60/65. Sunds Defibrator (now part of Metso) supplied the mill's original pulping plant.
Wood for the extra capacity is not a problem, according to Pijls. Lanaken sources its spruce from Belgium while its poplar comes from Belgium, The Netherlands, and France.
Previously, the mill had six refiners: three primary and three secondary, all in a row. The new, or seventh, refiner was installed at the end of the "street". In effect, it is a secondary stage refiner. There are now four primary stage refiners and three secondary.
Reconfiguring the process equipment and control system to accommodate the new refiner was a challenge. Each primary refiner does not have a separate preheater so one of the preheaters had to be modified so it could feed two refiners.
Two new dosing screw conveyors were installed. The new refiner meant another steam separator cyclone with a discharger was also needed. The existing dischargers of the six steam cyclones were replaced. This is because a higher quality plug is needed for poplar pulp. The cleaning system was extended from five to six stages.
In the control room, a complete renumbering of all the equipment was necessary. A new software program with new pictorials was also installed.
Some work needed to be done in the woodroom to handle the increased volume of wood. This included extending the log deck, installing an HQ chipper (replacing the old slicer), a new bark conveyor and speeding up the screw conveyors. Another important part of the project was the addition of a new pulp storage tank to handle the increase in poplar pulp capacity. A new 12-MW power line was also added. This necessitated a different feeding system from the main transformer to the CTMP plant.
Although the mill only needed an 11-day shutdown to install the new refiner, the project was brought into operation step-by-step from December 2002 until July 2003.
The first parts to come online were the improvements in the effluent treatment system in early 2003. The new pulp storage tower was ready by March. From June 24-July 4, the mill installed the new refiner, made the necessary modifications to the existing line and brought the expanded system online.
As the operators already had experience with CTMP, Sappi could keep the training to a minimum. As Pijls says, "The learning curve to make poplar pulp had been done before. Despite these quite extensive works, the reliability and consistency of the Lanaken qualities were never at risk."
Innovativeness handles increased COD load
An increase in BCTMP production means a subsequent increase in COD. To handle this and continue to meet emission standards, the mill installed a COD buffer tank (3,000 m3) to feed the COD load equally (before anaerobic treatment), increased its cooling capacity and installed a new aeration system.
The innovative aerobic purification system features turbines that add air to the water, increasing the efficiency of the treatment. The aerobic basin is divided into three sections and more air is introduced at the beginning. "This is a totally new development," Pijls says, "and we are very happy with it." If the mill had opted for a conventional system, Pijls says the capital and operating costs would have been much higher.
Rebuilt coater adds many benefits
What all this leads to is the production of 485,000 tonnes/ yr of coated woodfree and almost woodfree, as well as coated mechanical fine paper grades. The mill runs two paper machines: PM 7 and PM 8. Each has its own online coater and there is an off-coater serving the former machine.
PM 7 was originally installed in 1967 and last rebuilt in 2000. It has a 4.8 m trim and runs at 1,150 m/min. It produces 185,000-195,000 tonnes/yr. Installed in 1986 and rebuilt in 2001, PM 8 has a 7.4 m trim and runs at 1,350 m/min. Voith rebuilt PM 8's coater in 2002, using its JetFlow technology.
PMT Italia and Mitsubishi Heavy Industries have just completed a rebuild of PM 7's off-coater. The goal was to improve runnability and profile. Honeywell Measurex supplied the profiling system, the same that was installed during the rebuild of PM 8's coater.
The off-coater was from Beloit, with a Mitsubishi BA 1500 model coating applicator, installed in 1991-92 at the same time PM 7 was first rebuilt. Pijls explains that the mill had seen the benefits that could be realized from jet coating heads so PMT Italia installed its S Flow free jet applicators.
The rebuild allows Lanaken to reduce broke during a splice. Also, edge problems have been reduced, effectively increasing the width of the web. Coating coverage has also improved. Accessibility to the coater is better resulting in a much easier piece of equipment to operate and maintain.
Finally, Lanaken had PMT install a center drive system. If the mill wanted, the rebuilt off-coater could produce 200,000-220,000 tonnes/yr.
There were no changes to the coating kitchen or coating materials. Pijls stresses that the rebuilt off-coater and the new refiner were totally separate projects.
The successful completion of the projects gives Lanaken an extra degree of flexibility. It now produces 85,000-100,000 tonnes/yr of sheeted paper and about 400,000 tonnes/yr of rolls. Basis weights run from 60 to 170 g/m2. Pijls estimates that Lanaken produces 50 different grades - different basis weights, matte or silk - every 10 days. In a pinch, Lanaken has also helped out its sister Sappi mills during rebuilds or crises.
Lanaken's new Royal Xpress is a fine paper grade that uses a poplar BCTMP base. It comes in basis weights ranging from 70 to 150 g/m2. In general, low basis weight paper is made on PM 8, higher basis weights on PM 7. Pijls adds that Lanaken is the only Sappi mill in Europe that can produce lower basis weight papers.
Pijls says that Royal Xpress offers a great value proposition to its customers: good opacity and surface properties, also at the lower grammages. As BCTMP pulp is developed further, Pijls says it is becoming more popular as a substitute for chemical pulp. This stands Lanaken in good stead with its secure wood supply and know-how in the production of mechanical pulp.