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Why add organic biocides? Run cleaner from the start

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Why add organic biocides? Run cleaner from the start

March 11, 2012 - 16:00
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BRUSSELS, March 12, 2012 (RISI) -The Klingele recycled liner mill, near the North Sea in Germany, has proven that the elimination of traditional organic biocides lowers costs, improves productivity, and facilitates smoother operations of the wastewater treatment plant. Management has accomplished all of this with only one minor change-putting in place a compact on-line chlorine dioxide generator with multiple dosing points.

For more than 50 years, Klingele Weener has manufactured corrugated board base paper from 100% recycled fibers. Its papers provide the foundation for a wide variety of packaging and corrugated board products converted at seven locations of the Klingele Group for customers in Germany and abroad.

The Klingele production team has no tolerance for waste of any kind. They see recovered fiber as a valuable raw material, especially after undesirable dirt and stickies have been painstakingly removed.

The mill's biggest investment of the decade went into building its own electric power and steam generation system, employing refuse derived fuel to run the facility. Recently, it has focused efforts on cutting out organic biocides, which were negatively affecting the runnability of both the wet end and wastewater treatment in addition to contributing to higher chemical and energy costs.

Michael Goemann, wastewater treatment specialist

Decades of organic biocide usage

For many years traditional biocides were employed on routine basis to maintain cleanliness, but at a high price. Not only have biocide prices continued to rise, but more and more documented cases of their application contributing to off-quality production, over consumption of other chemicals, and instability in day-to-day operations on the paper machine and the wastewater treatment facility.

According to Uwe Sonntag, production manager at Klingele Papierwerke, "Why interfere with the stability of your papermaking process by adding costly biocides? Our switch to purifying incoming and process water opened the way for more consistent runnability, easier grade changes, and a lighter load on wastewater treatment."

Uwe Sonntag, production manager at Klingele Papierwerke, stands beside a creative example of their converting team’s work

Holistic view

In fact, when oxidative microbiological control of the paper machine circuit and anaerobic wastewater treatment are viewed in a holistic way, the potential is in place to adapt formulations to raise performance throughout.

Adds Thomas Wischeropp, mill manager at Klingele, "Because we regard ‘so-called' wastewater treatment as part of a unified paper producing system, we maintain pH level very precisely, and use pH variation as an indicator of potential trouble. This is critical to higher performance."

Notes Sonntag, "We have always sought to continuously improve by putting the latest technology, equipment and processes in place. After comprehensive trials, it became clear that a compact Purate unit, delivering low dosages of chlorine dioxide at nine strategic locations in the process, added a new dimension to cleanliness, and therefore, higher potential for stability and optimization."

Thomas Wischeropp, mill manager, and the Klingele team have benefited by optimizing the wet end and wastewater treatment system together

Life without organic biocides

Having used organic biocides for 20 years, Klingele understood their value, but also faced continuing higher costs. The mill really wanted to know how its system could run well without them.

Says Sonntag, "There's more to biocides than the biocides themselves. There are equipment issues, too. In the past many pumps for biocides were always running. We spent a lot of time dealing with totes, and safe handling of these chemicals. In addition, the time required to notate and monitor all the dosages was considerable."

Klingele investigated various alternative approaches with several suppliers. It considered distinctly different alternatives, including electrolytic activated bromine salts, ammonium bromide activated monochloramine (MCA)and chlorine dioxide generated by the Eka Chemicals Purate process.

During the investigation it became apparent quite quickly that electrolytic activated bromine salts could not fulfill the demands. Application of the monochloramine system caused a major drop in the efficiency of the anaerobic reactor. The compact on-site chlorine dioxide fulfilled expectations right away, and showed potential for other benefits.

Comments Sonntag, "After only a short trial period we quickly realized that Purate was the right choice for us. We now have a performance and cost advantage, compared with traditional biocides. Automated dosages allow us to reach the desired conditions on a consistent basis, and importantly, to maintain the pH within precise parameters."

AkzoNobel Eka Chemicals’ Christian Biermann and Wolfgang Correnz observe the Purate system, which eliminates the use of organic biocides

Increased demands on performance

Says Christian Biermann, AkzoNobel Eka Chemicals, technical manager Central Europe, "Klingele decided to take control of incoming and recycled water cleanliness in a profound way, and minimize impurities from wastepaper, polymers and starches. Papermakers are constantly confronted with issues like declining quality of recycled fiber, combined with the necessity to increase productivity. These factors require all kinds of innovations to maintain or raise the quality of paper and achieve energy efficiency throughout the entire production process."

Adds Sonntag, "Our team now has firm control of papermaking and anaerobic wastewater treatment as a single system, because we understand the importance of operating them in a holistic way. Consistent pH at the paper machine, matched by the same in wastewater treatment, represents the key guideline for us to watch. When pH is steady, other opportunities arise for further optimization."

Klingele Weener makes fluting and test liner from 100% waste paper, certified by the FSC Recycling Seal

Systematic dosing at the minimum

The Purate system at Klingele has nine dosage points, applying chlorime dioxide automatically, based upon established parameters, which are set at the lowest levels possible. Little time is required from mill personnel to monitor the system, as alarms are built in inform operators of a quirk in the process, as well as the Eka applications team via mobile phone.

An additional benefit has been the load taken off the wastewater treatment personnel.

Says Michael Goemann, Klingele wastewater treatment specialist, "When the pH is too low due to bacterial activities, water hardness increases because of formation of organic acids. This interferes with the efficiency of the chemical additives, causing a drop of the productivity, and a need to increase the dosages of expensive chemicals with little gain. By contrast, if bacteria growth suppressed, pH stays high, because there is only little pre-acidification in the paper machine circuit. We are steady at 6.8 pH now."

Goemann points out that water hardness does not increase under these conditions. Chemical additives work well and the productivity is high.

Also of note are time savings. Previously, it was necessary to dose frequently, and to manually record the dosages. More focus is possible on the wastewater treatment optimization, conducting other trials.

Adds Goemann, "When we don't have the pH swings in the waste treatment system, we have options for other kinds of trials. We continue to experiment to see what fits with the new system. And we are sleeping better at night."

Dosage points include direct injection dilution water, but also into the polymeric solution and into the starch.

Key Benefits
• Clean system and excellent runability of the PM • Reliable, stable pH adjustment by bacteria control
• Positive influence on chemical additives
• Prevention and/or reduction of the metabolism of the starch from the recovered paper
• Stabilizing influence on the waste water treatment plant, especially the anaerobic part

Decisive pH

The pH-value of the paper machine whitewater loop turned out to be especially decisive. Klingele was challenged to precisely adjust pH to a certain value and keep it constant with time and all over the paper machine circuit with a suitable biocide system.

Says Wischeropp, "We used to spend a lot of time dealing with paper machine stability. Now, our team is able to optimize paper machine runnability and wastewater treatment because of the efficiency of on-site chlorine dioxide generation, and the elimination of problems which arose from the use of traditional biocides."

Klingele considers on-line control to be a valuable asset. Says Sonntag, "If there is a minor issue, via internet, our Eka applications leader can see what's wrong, because the same direct alarms we receive through our process control system, he gets on his mobile. It makes a difference for us when the expert can make decisions on the spot, and is better prepared when coming to the mill.

"We have a better overview of this system. Operating costs were too high. Now we have only two tanks and one generator, compared to an array of totes at various locations, requiring a lot of attention."

Sonntag notes that "Anytime that handling of chemicals is minimized, it's a positive step for safety.

Creative ways to reduce

Seeking other creative solutions to make gains, Wischeropp has become a true believer in their new camera system to see where breaks are coming from. "Every papermaker should have this. Makes it easier to see where a break comes from. The original idea was to create specific ‘regions of interest' and mark them. Having set points, when something is different in the picture, you get an alarm. On the paper machine we think we get breaks from the approach flow system, perhaps deposits and impurities making their way onto the table, and causing breaks."

Sonntag adds, "Our silica nanoparticle system has made an important difference for dewatering, which allows for energy savings and higher output. Productivity is improved on line with a Kajaani system, where there is a set point for the white water, telling us to increase or decrease the amount of the nanoparticle or the polymer."

Over the past three years, Klingele has found several ways to achieve greater efficiency and flexibility. "Changing grades on short notice is the optimum response to meeting customer needs quickly," says Wischeropp. "The use of high-efficiency machinery at all stages of the paper-making process - from pulp production to the wire and drying sections enhancements- also strengthens our market position. Purate has been especially important for wet end optimization and better handling of wastewater." PPI

Martin Koepenickhas written about the pulp and paper industry for more than 25 years visiting mills