PPI Special Report
Jan. 7, 2013
Modern Karton Sanayi Ticaret AS in Corlu, just outside Istanbul, is the leading lightweight containerboard producer in Turkey and among the top six containerboard producers in Europe.
Modern Karton recently optimized PM 4. Changes in stock preparation and refining now allow operators to maximize a range of mixed waste grades and get much improved runnability on the machine due to cleanliness and a reduction in stickies.
Modern leap forward
A decisive move was made in 1998 with the beginning of a new age of containerboard production in Turkey, when Modern Karton led the way with the startup of PM 3, a 200,000-tonne/yr high-performance containerboard machine. Included in the delivery was a 100% recycled fiber stock preparation system to feed the hungry machine.
According to Ali Íhsan Aras, technical coordinator for parent company Eren Holding, "PM 3 propelled us into modern papermaking. Our portfolio of brown and white top grades was able to meet high European standards. We not only seized higher market share in our home market, but we gained business throughout Europe and the Middle East."
This success led to the launch of PM 4 in 2008, a machine which produces about 400,000 tonnes/yr of 70-120 g/m2 testliner and corrugating medium. Soon, Modern Karton will break ground for PM 5 which will add considerable lightweight grade capacity.
Eren Holdings' Osman Tamer, investment leader, says, "Turkey's growth in manufacturing consumes a considerable amount of our output, but we have also gained a stronger position in export markets. Our reputation for quality output is feeding our steady growth. And, our environmental stewardship ensures sustainability in support of major brands."
Overcoming operational difficulties
Back in 2008 when PM 4 came on line, Modern Karton began to expand relationships with global and local branders. The company had the infrastructure in place from collection-through-converting to move ahead rapidly. However, even though it was meeting customer needs, PM 4 had runnability issues, primarily due to stock cleanliness, which did not go away easily. Difficulties with the stock preparation equipment were making machine efficiency and productivity a challenge, requiring considerable ongoing maintenance.
Ramazan Tekin, production manager for PM 3 and former stock preparation manager for PM 4, says, "Stock prep was the primary bottleneck. Our maintenance team had to open up the screens several times a day to manually take away the clumps of fiber that were plugging the cylinders. Stickies were passing to the machine. Our OCC fractionation and fine screens had to be taken down for thorough cleaning every two weeks. Adding to this problem, we had to take PM 4's refiners offline. We were not able to achieve the gains in strength with these units and could only meet our customers' specifications with expensive starch and chemicals."
"Roping and plugging at the pulper were commonplace," continues Ilhan Koyunlu, production manager for PM 4. "We had too much unscheduled downtime for maintenance just to keep operating, and even then at considerably lower throughput than was our target. Energy consumption was too high. We had to make a strategic change."
Strategic change leads to major improvement
Modern Karton called upon Aikawa Fiber Technologies (AFT) for help with the stock preparation issues. Bulent Sendag, AFT's representative in Turkey, made the initial contact.
"AFT components can be fitted to all types of screens," says Sendag. "They produce cylinders, rotors, and plates for many major OEMs, so they have both a scientific and a practical knowledge of the stock preparation processes."
AFT specialists began an intensive study to determine the root cause of the stock preparation runnability problems. Two specific tools, AFT's SimAuditTM process simulation and a mechanical audit, were used in the analysis.
SimAuditTM is a proprietary process simulation tool which reveals in detail the potential for optimizing existing processes and sizing equipment. The mechanical audit determined the condition of the wear components to help AFT recommend a more effective maintenance program.
"When the internal components, rotors and cylinders, allow fiber to build up and plug the screen, there is no way a mill can experience smooth, continuous operation," Sendag explains. "The AFT audits revealed some good news for Modern Karton. The simulation showed that changing out the OEM wear components would allow Modern Karton to regain full capacity, and save energy."
A change for the better
The SimAuditTM revealed that smaller slots in the screen cylinders and a different rotor design would vastly improve operations. The Modern Karton team was very interested in the recommendation, but was hesitant to make such a change on all the screens. AFT offered a trial on just one screen so Modern Karton could evaluate the results.
At first, AFT delivered a MacroFlowTM cylinder with 0.20 mm slots, because this matched the OEM components. "The mill soon saw that our recommendation might be on-target and that smaller slots would improve stock cleanliness and stickies removal," says Sendag. So the slot size was reduced.
Capacity quickly returned to the targeted level. Stickies were no longer an issue, and energy consumption for that particular screen was cut in half. When the screen was opened after two weeks operation, there was no fiber/reject build-up at all.
That led Modern Karton to change all the rotors in its stock preparation screens to the AFT GHCTM model. MacroFlow2 cylinders with 0.15-mm slots are the new standard for PM 4 screens (with the exception of 0.17-mm slots for fractionation and long fiber screening).
Says Koyunlu, "Our maintenance team was able to turn their attention to fine-tuning other aspects of the process instead of babysitting the screens. We were able to improve sheet uniformity as well."
Solving the fractionation dilemma
As with most 100% recycled containerboard mills, Modern Karton has fractionation screens for short, medium, and long fibers. Rejects tend to concentrate in the long fiber fraction. It becomes difficult to separate the rejects from the fiber. That is why long fiber treatment is always the most difficult aspect of screening.
"With the AFT rotors and cylinders installed, we were not having the once-familiar stickies problems on the paper machine," comments Tekin. "The improvements in screening meant that we could eliminate rejects recirculation which had a big impact on the cleanliness of the stock to PM 4."
When the stock preparation screens began running smoothly, Modern Karton saw stability return to upstream and downstream processes as well. As Tekin puts it, "Stock preparation screening is now stable. The accuracy and precision of the MacroFlow2 cylinders at the smaller slot sizes have eliminated stickies as an issue for us."
Sendag notes that other issues like flakes can be handled in stock preparation, and prevented from going forward to the paper machine, where they tend to "open up" to become spots or defects in the finished sheet. "We are working now on the fundamentals of pulping AOCC and some other lower-grade local furnishes," he says, "by doing such things as reducing the gap between the pulper rotors and plates. Modern Karton is also considering installing outflow coarse screens to optimize deflaking."
New refiners end heavy starch doses
Once the quality of fiber from stock preparation was stabilized, Modern Karton decided to restart its refiners, to get the needed strength by properly preparing the fibers rather than relying on costly starch and chemicals.
Says Tekin, "With our stock preparation efficiency at a high level, we installed AFT Finebar® fillings on PM 4's conical refiners." The impact was dramatic. Strength targets were met immediately. Energy consumption dropped, and the mill was able to take its deflaker permanently offline.
The principal difference between Finebar and conventional plate patterns is the ultra-fine bar patterns which permit refining low intensity. This gentle handling not only produces desired strength and freeness, but reduces power consumption considerably.
Notes Tekin, "The Finebar patterns are very effective and the fillings are extremely reliable. We changed out all the fillings so that Finebar is on all our refiners on PM 4. Recently PM 3 began using them as well."
Next stop: Headbox screening
AFT has also been studying the potential to reduce slot sizes in top and bottom sections of Modern Karton's headbox screens. According to the AFT study, slot sizes can likely be reduced, especially for the top layer.
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