Ashland’s microbiological control technology has helped two Canadian mills increase efficiency and improve quality.
Holes, sheet breaks and myriad other sheet quality problems can be caused by dirty/clogged headboxes. Two Canadian mills, Tembec, Temiscaming, QC, and Smurfit-Stone,La Tuque, QC, were looking for a way to alleviate slime-related issues that necessitated frequentclean-outs. Tembec’s Paperboard Group’s (Temboard) mill produces 180,000 tonnes/yr of various paperboard grades used in lottery tickets, point of purchase displays, cereal boxes, calendars, tobacco packaging and gum wrapper to name but a few.
The mill opted for an Ashland Hercules Water Technologies microbiological control program using Spectrum XD3899 ammonium bromide technology (see Pulp & Paper, November 2004, p. 45). Although this patented biocide has been used for many years by numerous mills in the United States, Europe and Latin America, it was only recently approved for use in Canada.
Part of Tembec's continuous improvement.
Temboard mill manager Lori Kilgour said the decision to use the biocide was part of the mill’s history of continuous improvement. “We are always trying to get better. We did have some cleanliness issues in the headboxes and we were trying to solve that.” Marc Gamache, wet end superintendent, explains that the machine has top, filler and back ply headboxes. Every three to five days, the machine was suffering breaks because of stalactite-like accumulations dropping into the stock flow from the top of the slice lip of the top and bottom headboxes, causing holes and coater breaks. “We had to stop the machine, open the slices and clean out the accumulation. There were also large accumulations in the pan underneath the machine.” An analysis of the deposits also showed a lot of starch, which s a good food source for microbiological organisms.
The mill had looked at various options: coating the inside of the headboxes, improved screening, and additional feed points with the existing microbiological control program, before opting for Ashland’s Spectrum XD3899 technology. The trials came about because, as Kilgour puts it, “Jim kept pounding on my door.” “Jim” is James Syncox, Ashland’s sales team leader. “We knew we had to make a change and trials are an essential part of continuous improvement for Temboard. ”Trialing began in November 2008 and went through July 2009. The trial lasted nine months for a number of reasons. The mill makes a lot of grades and it wanted to get through the spring when run-off from the thaw can create water issues in the mill. Also, it wanted to go through grade change cycles and boilout cycles. The XD3899 program resulted in a number of improvements. Previously, the mill had two large broke towers that it needed to operate and maintain. Now, with the machine running much better, it only needs one broke tower. The mill has also been able to reduce its wet end chemical use while running to the same white water targets.
The crews took notice.
The cleanliness of the machine was perhaps the most noticeable difference to the crews. They said they had never seen the machine so clean. Previously, the mill performed a once-a-shift cleaning of the save all. If this was not performed, the saveall would be very pink, a sign of microbiological growth. A lot of microbiological growth was occurring in the broke. That has also improved significantly. Optimizing process performance with the Ashland technology required adjustments. Technical superintendent Anne Rivard explains that the trial was started with predetermined feed points for the new biocide. “With monitoring, we saw that we had to feed at different points and at different doses.” The dosing equipment (see sidebar) was provided by Ashland but the Temboard crews did the piping work and now maintain it. “For the trial,” Rivard continues, “we monitored downtime as it related to microbiological growth. We reduced that by 49%.” In all, the mill equated the gains to a 1% increase in operating efficiency, which is significant. It’s no surprise that Temboard converted to the Ashland system on a permanent basis. The mill has noticed a drop in sheet breaks, perhaps one every 10 days, a reduced number of holes in the sheet, fewer culls related to sheet contamination and reduced washup time on breaks. Kilgour says customers have also noticed the changes. One had issues with runnability. Now, they are very happy and ordering more.” The mill now runs longer between boilouts. In the past, when the boilout date was reached, the machine was also very dirty. Now, it is still relatively clean. Rivard notes that Temboard is taking a cautious approach to boilout frequency. “We feel it can be extended, but we want to go slow. Over the long-term, we now believe maintenance and corrosion issues will not be a factor. There will be big payoffs over the long run.” Enhanced safety is another benefit for the maintenance crews since the XD3899 dosing system only produces biocide when it is needed. Additionally, when the treatment is complete, the biocide line is automatically flushed with water, ensuring no standing biocide remains in the line Although Temboard did some other work on the machine, including changes to fresh water treatment, machine clothing adjustments and wet end automation, Kilgour said the benefits cited can be attributed to the XD3899 technology. Overall, machine efficiency has improved more than 1%, which has led to increased productivity, improved quality, lower costs and improved safety. Temboard is currently running a 12-week trial with Ashland’s XD3899 technology in the starch system. “We are looking for the same benefits,” Kilgour adds. “We run a lot of starch, three different types, so treatment is critical. If this trial is successful, we will be able to eliminate a strong oxidizer (used for microbiological control) we have on site.” Technology alone is not enough. Kilgour says one of the main reasons for success is the team at Temboard. And, Ashland brings a lot to the table. “They work well with us and work hard to improve Temboard’s performance. Ashland has an excellent support team.”
-Article recreated from Pulp and Paper International Magazine (www.risi.com, February 2010, pp 31-33).
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