FOCUS:

By MONICA SHAW, Executive Editor

SP Newsprint Co. - Running With The Best At A Mile A Minute

MONICA SHAW
is Executive Editor
for Pulp & Paper
Magazine

Running at an average speed of more than 5,400 fpm with efficiencies greater than 90%, the No. 2 paper machine at SP Newsprint's mill in Dublin, Ga., is the fastest newsprint machine in North America and the third most productive newsprint machine in the world. Achieving such an enviable international standing, in a group where no other North American machine makes the top ten, requires an organization focused on continuous improvement, an extremely stable process, and investment in cutting-edge technology.

To run with the best, SP Newsprint has continued to address bottlenecks on the No. 2 paper machine since its startup in 1989. Recently, the mill rebuilt the No. 2 paper machine to include a shoe press—the first such installation for newsprint in North America. To support the extremely fast speeds available from the new press, the Dublin mill also had to improve the quality of its deinked pulp and boost pulp production.

SP Newsprint Co. is a partnership between Cox Enterprises, Knight-Ridder, and Media General, each of which owns one-third. These owners consume approximately 40% of the Dublin mill's production. In an era when many paper companies have reduced capital spending to improve returns, how was SP Newsprint able to convince its owners that the $25-million project, carrying some technical risk, was worthwhile? To Mark Rawlings, SP Newsprint's senior vice president for the Southeast region, the decision was based on company strategy, an excellent track record with capital projects, and future stability.

"Obviously, with more tons you can distribute fixed costs, producing a more reasonably priced product," describes Rawlings. "But we also know that our assets have to be as cost-effective as possible for long-term survival in the newsprint industry, and our owners do have such a long-term view. Fortunately, we have historically provided a good return on capital by choosing the right projects, which was again the case with the latest rebuild."

Attaining the North American speed record of 5,513 fpm on May 23 of this year required more than two years of optimizing the technology after rebuild completion in July 1998. It also required a cultural shift based on attention to detail and sound papermaking practices.

"You have to learn a new set of rules when you transition from 4,200 fpm to 5,500 fpm, and it's a tough world to walk into," explains Jack Carter, Dublin mill manager. "For efficiency, this machine requires consistent and clean pulp, along with good paper department housekeeping. Constant attention to detail is necessary, which requires the tools allowing operations and maintenance groups to take a more sophisticated look at the process and its control. And, to run this fast, you have to build confidence and define what conditions work best with your operators, which takes time."

NO. 2 PAPER MACHINE EVOLVES. In 1989, the 358-in.-trim No. 2 paper machine started up, achieving 4,000 fpm within just weeks. The machine featured a Valmet SymFlo HS headbox, SpeedFormer HS (twin-wire) former, and a SymPress O press section that provided the option for a fourth press. The dryer section included three UnoRoll single-felted groups and four double-felted ones, with a breaker stack between the sixth and seventh sections. Drive design speed was 4,500 fpm. Also installed were a conventional hydraulic reel and a two-drum winder. In addition, a new deinked pulp line and a cogeneration plant were built to support the No. 2 machine project.

A third winder was installed in 1994. Although it supported both paper machines, the winder primarily enabled a 200-fpm increase for the No. 2 paper machine. In 1996, the first three dryer sections were converted from UnoRolls to VacRolls (vacuum on bottom rolls), boosting speed to 4,500 fpm. Other upgrades included changing from a granite center roll in the press section to ceramic.

Rawlings is quick to point out, however, that improvements during the 1990s were not solely focused on increasing speed. Although SP Newsprint's sheet provided good printability, partially due to the twin-wire forming process, its pressroom runnability was somewhat inferior, as company owners indicated. Contrib-uting to this was the Dublin mill's use of older, washing deinking technology that did not tolerate magazines in the old newspaper (ONP) furnish. In 1996, the company began an ISO 9002 quality initiative that included incorporation of on-site ONP sorting at the mill to reduce contaminants in the furnish.

At the same time, interest had grown in further speeding up the No. 2 paper machine. The press section was the next bottleneck, and the decision to upgrade it revolved around adding a fourth press or looking at shoe press technology for the third position. In August 1996, a team from the Dublin mill toured European shoe press installations for printing and writing grades, as well as the sole newsprint machine using the technology in Braviken, Sweden.

After the tour, Rawlings reports that SP Newsprint "didn't feel there would be a huge degree of risk with shoe press technology over adding a fourth press," although it would be the first newsprint machine rebuilt for one. Improved speed could provide the owners with a secure, long-term supply of newsprint, but would investment in such a new application prove too risky from a return standpoint?

"Their primary business is publishing newspapers, but they also look at us as a high quality newsprint supplier and a profitable business entity, so they expect positive results," describes Rawlings. "We provide enough newsprint for them that you might consider it a supply security hedge, but I don't think they would re-tain us if we weren't producing good returns, regardless of how much newsprint they purchase from us."

In late 1996, SP Newsprint received approval for the $25-million project, which included deinking plant upgrades. The capital request stipulated a rate of return for the owners, and, because the rebuild project would increase recovery of ONP, SP Newsprint was able to qualify for tax exempt bond financing.

Metso (formerly Valmet) was chosen as equipment supplier for the shoe press portion in January 1997, while Ahlstrom would supply deinking improvements. One primary concern related to the shoe press was how the Dublin mill's furnish would run at higher speeds, since washed deinked pulp carries forward more residual ink and contaminants than flotation deinked, although this problem had somewhat been addressed with improved sorting. SP Newsprint's contract with Metso included warranty provisions for speed, dryness after the press section, productivity, and finished sheet quality parameters.

MORE PULP FOR THE REBUILD. Since startup of the No. 1 paper machine in 1979, SP Newsprint has used a patented washing deinking process licensed from Garden State Paper. Even at the 800-tpd capacity prior to the rebuild, the No. 2 paper machine's deinking plant was already at maximum capacity, so another deinking line was needed to make the additional 80 to 100 tpd targeted on the No. 2 paper machine. But, would the line use a washing process or a more contaminant-tolerant flotation process?

"Washing actually ended up being the most capital intensive, so it became a matter of affordability," explains Rawlings. "We knew there was more technical risk with mixing a flotation line with our washing chemistry, but it's come pretty close to meeting expectations. At 20% to 25%, fiber loss is high compared to traditional flotation deinking, but this was the trade-off we accepted to keep cost down and to allow the system to work inside existing process water loops."

The new 150-tpd Ahlstrom flotation system was installed during June 1997. In SP Newsprint's process, ONP is deposited into a bank of three continuous pulpers that feed two dump chests—one for the No. 1 deinking line and another for the No. 2. On the No. 2 side, part of the stock bypasses the washing line and goes to the new flotation system. Afterwards, this stock is thickened and mixed back with stock from the No.2 washing line before it reaches the wet end of the No. 2 paper machine.

About 3.0% to 3.5% ash comes in from the ONP, with another 1.5% added just before the paper machines in the form of calcined clay to achieve opacity targets.

Is there any real market advantage for running 100% recycled furnish? Not as much as in the past, according to Rawlings.

"Earlier, we had problems with contaminants and stickies, but if you look at our pressroom statistics today, our customers would say it doesn't matter that it's a 100% recycle sheet," states Rawlings. "In the 1980s, many states legislated minimum recycle content, and that provided us some market advantage. Today, customers look at product quality and the total package offered. Also, with more mills using recycle content, ONP prices have gone up while the quality generally available on the market has deteriorated."

To further improve quality, SP Newsprint is installing a thick stock screening system on the approach to No. 2 paper machine wet end this July. It will feature 0.006-in. slots. In addition, after successful implementation on the whitewater system of the No. 1 paper machine, a new ink and contaminant removal system will soon be installed for the No. 2 machine. The system was patented by Alan Lawson, an engineer at SP Newsprint.

FLAWLESS REBUILD PROJECT. SP Newsprint's rebuild project for the No. 2 paper machine was completed during 14 days in July 1998. According to project engineer Rodney Allison, who is now the process manager for the No. 2 machine, the installation phase of the project was "pretty flawless" from a mechanical and structural standpoint, although problems related to hydraulics appeared after startup. BE&K served as the engineering and construction contractor for the machine rebuild project, which included significant changes to the press section and dryers.

New shoe press. In the rebuild, the entire third roll nip press was removed and replaced by a Metso SymBelt II shoe press installed at a 26† angle (Figure 1). At a maximum of 5,700 pli, the high load of the new third nip required a new, internally-loaded Sym ZLC ceramic center roll. In addition, a drive upgrade supplied by Metso and Reliance to support 5,200 fpm was incorporated.

Dryer. The fourth dryer section was converted to single felting and the bottom dryers to VacRolls. In addition to the fourth section unirun conversion, all dryer felt stretch rolls were changed to reduce vibration at the higher speeds. Significant dryer section drive changes were made to accommodate the 5,200-fpm design speed, and many drive points were upgraded for speed and horsepower.

Other improvements. A new drive point was added to the former to support higher speeds, and HiDry fabric cleaner was implemented on the inner wire to help with contaminants. Also, due to higher speeds and vibration concerns, a new Tailjet (water jet) tail cutter was added to help with threading.

Process control. Although the No. 2 paper machine still uses its original Foxboro DCS, new control strategies were incorporated to support the new equipment. While not part of the rebuild project, several other control improvements have been and are in the process of being added to the machine.

For example, the No. 2 machine has laser center roll draw control that is allowing the mill to experiment with some closed loop strategies. The laser measures center roll sheet release or "draw" on the shoe press and feeds the information to the DCS for control of a drive motor downstream, which speeds up or slows down as appropriate. Carter notes that this application is "proving to be very beneficial." He also mentions that "a multivariable approach is being tested for making automated process changes upstream in an effort to keep the release properties from changing."

DRIVING THE RACECAR. In July 1998, the rebuilt No. 2 paper machine started up at 4,300 fpm, achieving 4,700 fpm in a matter of days. At startup, loads on the new shoe press were 3,700 pli, which soon rose to 4,100 pli. Despite a fairly smooth project and startup, SP Newsprint quickly found that the real test was learning to run the equipment at the high speeds it could support. As Allison notes, "Installation was a piece of cake compared with the aftermath."

The Dublin mill also learned that the fears it had in advance relating to newsprint quality were not going to be the major impediment to running a world-class machine. Nor was the life of the shoe press belt, which ultimately only required changing every six months. The unanticipated problem ended up being a mechanical one associated with the shoe press that took a year to isolate and correct.

Solving the shoe press problem. The shoe press problem occurred sporadically, causing a wet front edge on the sheet, making the machine difficult to thread without breaking. The mill could get rid of the problem by unloading and reloading the press several times, but the problem showed up almost every time the machine shut down and started up. However, the press would sometimes run for months with no problem and then "take a nosedive," describes Allison.

Removal of the shoe sleeve in October 1998 showed problems with friction and binding on the front edge of the shoe, impacting the loading profile throughout the press since the shoe would not stay aligned with the center roll. In talking with other mills with shoe presses, SP Newsprint soon found itself "on its own with a unique problem," says Allison. Working closely with on-site representatives from Metso, the mill and its supplier designed a fix by March 1999, although it would not be installed until a July 1999 scheduled shutdown.

The fix involved adding a centering key to prevent sideways movement in the shoe, as well as installation of a redesigned shoe plate assembly. Currently, the mill is getting 48% solids off the center roll—a "necessity" for the mill's furnish, which Carter still describes as "somewhat dirty."

Quest for speed. While the fix corrected the major problem associated with startup, the mill would have to continue making changes to achieve world-class speeds. For example, a high vacuum flat box has been installed on the conveying wire of the former as a substitution for the secondary couch roll. Combined with headbox changes, this has boosted solids off the wire from 15% to almost 18%. Such changes may also allow more water in the headbox to support a higher jet-to-wire ratio found in lightweight coated grades.

Also, in August 2000, the mill changed the center roll cover material and added doctoring equipment, as well as a new style of shoe blanket with a grooved shape that resists collapsing under higher loads. Afterwards, sheet breaks dropped from an average of 7 to 10/month to between 4 and 5/month, improving machine efficiency. However, according to Carter, it's often difficult to pinpoint the exact adjustment causing improvements.

"We might change many things at once just to get out of a problem," notes Carter. "We often don't have enough time to more scientifically try one and wait. At these speeds, the process can be very unforgiving and you can quickly go from making paper to not making any at all, without really knowing why. There's just no room for error at high speeds."

One area of experimentation has been with loadings on the shoe press, which proved a bit confusing at first due to the initial mechanical problem.

"Even though our shoe press has the capability to go to 5,700 pli, we haven't seen that it's advantageous to run that high," explains Carter. "That could change as we continue striving for improved efficiency and speed, but, at this point, we're typically running at about 70% of load capacity."

SP Newsprint continues to identify each problem with the No. 2 paper machine, no matter how seemingly insignificant. For example, the mill is looking into a skewing problem on the first press that is masked by the second and shoe presses. Specific emphasis is now on fine-tuning control equipment—from temperature and pressure to shoe press center roll draw control.

Efficiency is key. Late 1999/early 2000 marked some of the "more painful parts of the learning curve" with respect to gaining speed, says Rawlings. However, as Figure 2 shows, average reel speeds have continued to steadily climb since the rebuild was completed. As Figure 2 also shows, efficiencies were harder to build but have led to SP Newsprint's ranking as the third most productive newsprint machine in the world, according to data from the Pulp and Paper Products Council (PPPC). The data shows SP Newsprint as the only North American machine among nine European ones in the top ten.

"By just running fast, quality was suffering, and the machine was haying out," explains Carter. "In 2000, we started running for efficiency and then built up the speed. If you don't, something costly will eventually tear up. There's so much kinetic energy stored in that machine that, under the right circumstances, it can be almost like an explosion if something gets loose and things fly apart."

The No. 2 paper machine currently has an average monthly speed of 5,430 fpm. In May 2001, the machine hit just over 5,500 fpm, with efficiency holding steady at just over 90%. However, Carter says, "There's no room for error, or we'll be potentially sixth or seventh" in the international productivity ranking. He notes that the machine has been tested at speeds of 5,750 fpm, although running at that rate would likely cause the mill to reach pulping capacity limitations. "But we'll be looking for ways to go there some day," he states.

WALKING INTO A TOUGH WORLD. For operators and managers alike, attaining the North American speed record and international standing has truly been a "tough world to walk into," as Carter describes, noting the "tired, tough times" during the more than two years of working through problems with the shoe press and center roll release. "It is a testament to our folks that they kept trying to make things work throughout that time," he emphasizes.

Most operators for the rebuilt No. 2 paper machine had come from the No. 1, and doubts about runnability after the rebuild ran rampant when the No. 2 machine had many problems with the stock—problems that could not be corrected with the old techniques.

"I guess there was a feeling among folks that it would just be easier to stay at a comfortable speed, but that was not our vision," describes Allison. "We struggled to learn to run this machine—not only the new press, but with speeding up our stock system and deinking plant. It was just so hard to realize the significance, just after startup, of running 800 fpm faster than the No.1 machine."

Living with a slim margin for error was just one adjustment. Many times, studying trends from instrumentation would not yield a clue to problem sources, leading to "trial and error" stumbles. However difficult, Rawlings reports that working through the problems has led to a "growing feeling in the workforce that they can be winners with international significance."

Carter agrees, pointing out that letting all within the mill know about speed records is probably not even enough. "We also make shorter, more specialized runs than many in the top ten," he remarks. "So, everyone's doing a better job than reflected solely by speed."

NOWHERE BUT UP. Despite a bumpy market, Rawlings reports that the rebuild project "has met or exceeded the hurdles" promised to SP Newsprint's owners from a financial standpoint. In addition, Carter notes that the discipline required for running at such high speeds has translated to a higher quality product, which is "favored as a front page for many newspapers."

"To run better, we need better profiles, a stronger sheet, less water absorbency," explains Carter. "Everything we need, our customers need. So, we firmly believe that if we make the paper machine run better, it improves the runnability of our product for customers in the pressroom."

Future technical hurdles. "We will continue to strive to find a way to perform better," states Carter, noting that the No. 2 machine is "not too far away from being as productive as state-of-the-art allows." Supporting this statement is a variety of concurrent projects for further optimizing the No. 2 paper machine.

For example, a BTG online freeness measurement system was installed on the wet end. The system will be used to drive control strategies for combating quality inconsistencies originating in the deinking plant that affect freeness. Control schemes for this system have been evolving for the past 10 months. Additionally, a Metso Kajaani RM 200 online retention measurement system has been purchased to monitor ash content on the wet end.

A new online basis weight, caliper, moisture, color, and ash measurement and control system from Honeywell Measurex was started up this May, with scanners at the reel and breaker stack locations on the No. 2 paper machine.