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Oulu’s PM 7 sets world speed record less than one year after start-up

Making fine paper is still an art. When Veitsiluoto Oy (now part of Stora-Enso) started up its PM 6 making fine art papers, “The art of making paper” was its campaign slogan. Now, just six years later, the Oulu, Finland, mill has completed another ambitious project, Lumi 7. The company left no stone unturned in ensuring it would provide the market with the highest quality paper possible.

Although its appears identical to its sister machine, PM 6, do not be deceived. There are many important differences. Still, having two start-ups in such a short time did have its benefits. For example, many people from the start-up crews (consultants, suppliers and mill) worked on both projects. The processes and product, although not identical, were similar to those of PM 6. The big benefit, according to production engineer Tapio Kraatari who worked on both start-ups, was that, “We knew what could go right and what could go wrong.” Also, the crews concentrated so hard on making PM 7’s start-up successful, that they did not “fall into the trap of thinking about PM 6,” he added.

The then-new PM 6 was detailed in the pages of PULP & PAPER CANADA, December 1995. Then, Veitsiluoto Oy had just announced a merger with Enso-Gutzeit that was approved in 1996. Plans were also announced for the 2.5-billion Finnmark (approx. CDN$1.8 billion [1995 dollars]) PM 7. Of course, in 1998, Enso merged with Stora to form (at the time) the world’s largest forest products company.

Start-up of PM 7 was scheduled for the end of May in 1997, but the project was completed ahead of schedule and the first paper came off the machine in April 1997. Kraatari credited another new technology with helping advance the start-up: the mobile telephone. There was instant access to everyone involved, no matter where they were. “We figured it helped save a few days in construction.”

Although PM 7’s design capacity is 382 000 tonnes per year (t/y), in effect, the new machine raised mill capacity by 450 000 t/y. Is this the new math? No. PM 7 will concentrate on the lower basis weights of the high-quality printing papers (LumiSilk and LumiArt) that the Oulu mill makes. These basis weights will range between 80 and 118 g/m2. End uses include annual reports, advertising inserts, direct mail and magazines that need a high-quality paper. PM 6 will produce papers with higher basis weights, up to 216 g/m2. A laminator installed with PM 6 can bring the basis weight to over 400 g/m2. In effect, this has raised PM 6’s production by 70 000 t/y, to 420 000 t/y.

Although PM 7 can make 382 000 t/y, the machine is not scheduled to reach its design capacity until 1999-2000, less than two years after start-up. Budgeted for 136 000 t in 1997, it reached 160 000 t. The 1998 target was about 300 000 t.

The extra pulp demand was handled within Enso. Oulu did not have enough hardwood (birch) pulping capacity so some is purchased from other Enso mills such as the Enocell mill in eastern Finland. Oulu used to market some of the softwood pulp it made; about 85% is used in-house now. Pulp supply and paper machine demand are in balance.

Pulp furnish demands on basis weight and customer specifications. The lower basis weight papers are about 50:50 hardwood:softwood. The heaviest paper from PM 7 is 40% softwood, 60% hardwood. All pulp is ECF.

A certain amount of filler — precipitated calcium carbonate (PCC) and ground carbonate — is added to the furnish depending on the grade. The PCC is made at Enso’s Kemi mill and shipped to Oulu.

Lumi 7

The entire production line for the project is called Lumi 7. Besides the paper machine, coater, winder and related finishing equipment, the mill also added new stock preparation facilities and a coating kitchen. Installed in one continuous line, the equipment stretches for 1.2 km.

Ahlstrom Machinery supplied the paper machine approach, filler and broke recovery systems. The former includes a Multi-Retention Deculator, an AhlCleaner TC133 cleaner plant and MODUScreen H screens. Filler is recovered with a FilRec system. It recovers 66% of coarse filler and filler flakes.

Kraatari said that pulp quality is good and that not much treatment is needed. Sunds Defibrator Conflo refiners add the final touch. Pulp blending and filler addition is done by the paper machine crews.

As per PM 6, PM 7 is a Valmet machine from stem to stern. It features a Sym-Flo headbox and the horizontal high-speed (HHS) former and a long nip (shoe) press (3-nip SymPress B). Wire width is 9 m and design speed is 1600 m/min. (In June, the machine was running about 1300 m/min.) It is officially the fastest fine paper machine in the world. Over a 24-hr period on February 2, 1998, the Lumi 7 production line averaged 1330 m/min. In November 1998, the mill bettered that record, averaging 1430 m/min over a 24-hr period. The coater also set a new speed record — 1800 m/min during one machine reel. In that time, it had three grade changes. Three changes is the daily average, but changing grades is not the biggest adjustment for the machine; going from matte to glossy is because a coating adjustment is needed, Kraatari explained. Even then, the machine is not stopped because the control system can handle the change.

The Sym-Sizer on PM 7 makes the first double-sided precoating. On PM 6, it only applies starch. Thanks to the shoe press, PM 7’s dry solids content is 2 to 4% higher than that of PM 6. Stiffness is also higher. Kraatari pointed out that although the machines look alike, there are many critical differences and those involved with the project couldn’t automatically think about PM 6 when working on the Lumi 7 project. “The technology evolves so quickly,” he noted. “There was only six years between the machines, but its different technology.” PM 7 is also designed especially for lighter weight grades.

Although everything is being done to prevent breaks, if they do happen, the mill has a Hilcont 500 paper monitor inside the machine with 12 high-speed cameras. An identical system is also installed in the coater. “It’s very useful because of the speed of the machine,” Kraatari said. “If we had a break, without the cameras we could not see what happened.”

Moving towards the dry end, the OptiNip pre-calender (soft calender) imparts surface characteristics needed for coating. It can run at a maximum liner load of 250 kN.m.

PM 7’s OptiReels can build parent reels up to 3.4 m in diameter, weighing about 80 t. (Each reel can hold 100 km of paper.) There are four OptiReels: paper machine, re-reeler before the off-machine coater, coating machine reel, and re-reeler before the OptiLoad calenders. The mill has had no problems with the king reels and Kraatari credited this to the reelers which are “really working properly.” The large reels mean there is less splicing in the coaters and, therefore, less risk of break.

Opting for OptiCoat

Whereas PM 6 uses Valmet’s Autoblade coating system, the mill chose OptiCoat technology with OptiJet coating stations. The four-station off-machine coater has a web width of 8.44 m and a design speed of 1800 m/min. (In June, it was running between 1300 and 1500 m/min.) Compared to traditional technology, one of the main advantages of the OptiCoat system is that the web is not wet as per an applicator roll. This results in fewer breaks. The Jet coaters are easy to use and maintain and give an even profile.

The coater is the world’s fastest and must be shut once a day to allow the paper machine to catch up. When the paper machine is up to design speed, they will be in balance. The coater stations must be cleaned “every so often,” Kraatari added, but then, coater speed can be increased.

Valmet-Raisio supplied the coating kitchen, the world’s largest in terms of capacity. It included a pigment storage area (common with PM 6), coating color preparation equipment, off-machine coater’s four circulation systems, surface sizing starch treatment, paper machine pre-coating circulation and wet end chemical systems.

Pigments are brought to the mill in ships designed especially for this purpose. They arrive once a week carrying loads of betw
een 5000 and 9000 t. The major pigments are carbonate, clay and latex (for binders). The mill uses ultrafiltration on the pigment wastewater when cleaning coating stations and tanks. This is a new Valmet-Raisio technology.

The Oulu mill is the first to use the OptiLoad calenders. Two are installed; the first was installed in December 1996 and reels from PM 6 were tested on it. A new loading principle along with Dura polymer rolls, reversed roll stack order and increased process temperatures are said to give improved calendering performance and flexibility. On reason for the OptiLoad choice, noted Kraatari, was that the mill did not want to separate matte and glossy production runs. (PM 6 has two calenders for glossy grades, one for silk.) High end quality was also a reason for the choice. “We can achieve the same gloss and smoothness while, at the same time, obtaining improved bulk and opacity.”

There are two JR 1000 E winders and one WinBelt-MR rewinder. Rolls are brought to the rewinder by a Rocla AGV (automatic guided vehicle) system.

Paper machine runnability and paper quality are excellent. Compared to PM 6, runnability is especially important as PM 7 is producing lighter weight grades. “The customers are happy and so are we,” Kraatari added.

Handle with care

With the new machine, the mill doubled its sheeting reel storage capacity, adding a new crane. Once the rolls are conveyed from their respective machine rooms, they are put in the common storage area. Oulu uses Rocla laser-guided robot trucks to move the rolls to the sheeters and/or wrap lines and then to shipping. They cradle the roll during pick-up preventing damage.

Sheeting capacity was doubled with the addition of two new Bielomatik sheeters. The new sheeters have seven unwind stands versus six on the older models. The new sheeters handle reels from both machines. PM 7’s production will be split evenly between sheets and rolls. PM 6 will be 80:20 sheets:rolls. There are four ream wrapping machines. The sheeting plant also installed a new Vesme packaging line, Bielomatik wrapper and a Wrapmatic ream wrapper. No new roll wrapping equipment was needed. There is one cartonizer. It is used for US shipments to prevent damage.

Most of the three-quarter million tonnes produced annually leaves for Europe directly from the mill’s port. Three new ships were built for this purpose. Every week, four ships leave Oulu for Germany, Belgium and/or the UK. The rest of the paper is sent by rail to Helsinki and shipped overseas from there (Oulu’s port is not big enough to handle all the production.), or sold locally.

The majority (67%) of PM 7’s product is used in advertising materials. About 25% is used in book and magazine publishing while the rest is used for various brochures.

Complementing the Valmet paper machine is the Valmet Automation Damatic distributed control system.(DCS), XIS information system and PaperIQ quality control system. PM 6 has a similar system and one display terminal in the both of PM 6’s control rooms was updated to match that of PM 7 and allow a cross view between machines.

As can be expected, PM 7 is highly automated. There are 15 500 direct process interfaces for process and machine control. In addition, there are series interfaces to other control and measurement systems. Complementary Valmet Automation equipment includes Kajaani wet end retention measurement equipment as well as a Sensodec runnability and condition monitoring system (paper and coater).

There are five control rooms: coating/color kitchen; base paper; supercalendering; winding; and rewinding.

Also in the process end, Measurex supplied a fault detection system. Neles Controls was chosen to supply 1500 automated valves (500 control, 1000 on/off). Twenty-five ND800 valve controllers were included in the order. The controllers take the place of traditional positioners and are used in potential trouble spots. The controllers also record valve performance in detail, an important predictive maintenance tool. Valves do not need to be removed to check on their condition.

Due to the demands of the customers and the end uses of Lumi 7 paper, testing is an important part of the process. One sample is taken from each reel; samples are taken after the paper machine, coater, winder and supercalender. One piece goes to the light table by the paper machine and one is sent to the lab. Two Lorentzen & Wettre paper testers (one for base, one for coated) test gloss, smoothness and other properties. It takes 50 measures per sample and takes 15 minutes. The information is sent to the control rooms by computer.

Oulu also installed a five-color printing press. As Kraatari explained, the “eye” is very important. “The paper may meet all the design specifications, but how does it look when it’s printed?” The printed samples are studied every shift and during the morning production meeting to see if process changes are needed.

Crews on PM 7 are a blend of new employees and people who worked on PM 6. The new employees were hired at least a year before start-up and worked on PM 6. When PM 7 started up, the mill designed its paper machine crews so that each machine’s crews would be a blend of new and experienced hands.

The training effort was a combination of in-house and supplier courses. Kraatari noted the mill is taking the first steps towards the team concept for all production lines for both machines.

Specialized needs

PM 7 is shut every third week for 10 to 12 hours for routine maintenance. PM 6 and 7 are not shut together for these maintenance breaks. In all maintenance shutdowns, some paper machine clothing is changed. Because the machine is still new, not many rolls have been changed. Kraatari expects more roll changes in the future as their running time increases.

There are two major maintenance shutdowns per year, midsummer and Christmas. During these three, to four day breaks, both machines are down. There is some outsourcing of services. “We don’t have enough people for this type of shutdown,” Kraatari explained. “The specialized maintenance techniques needed are easier to buy than to learn.”

Valmet Automation people are on-site permanently, particularly for the PaperIQ system. “There are a few others,” Kraatari added. “This looks like the future.”

Sailors still happy

There was an increased load to the mill’s effluent treatment facility and some changes were needed to meet the increased demand, but Kraatari noted, the nearby yacht club is still happy with conditions. Sailors must pass by the mill on their way to open water. Only 10 m3/t of the mill’s wastewater requires treatment prior to discharge.

A new power boiler was also installed, not just for PM 7, but to supply the entire mill with steam and electricity. Supplied by Tampella Power (now Kvaerner) the boiler can produce 246 MW and 95 kg/sec of steam.

As noted in the 1995 article, the mill did not want to rest on its laurels. The success achieved with the Lumi 7 project shows it did not. A release issued by the company after the speed record was set noted that: “in terms of daily production, the learning curve has been the best achieved on Valmet woodfree paper machines, at any time or place.