Research & Innovation
MECHANICAL PAPERS: Success Through a Continuous Development of Process Know How and Production Efficiency
By Pulp & Paper Canada
Sweden-based Holmen Paper is a Scandinavian supplier of mechanical printing papers with an annual capacity of 1.7 million tonnes. The company is a quality leader in Scandinavian newsprint production. ...
By Pulp & Paper Canada
Sweden-based Holmen Paper is a Scandinavian supplier of mechanical printing papers with an annual capacity of 1.7 million tonnes. The company is a quality leader in Scandinavian newsprint production. It is also a forerunner in developing new uncoated mechanical grades. The company has continuously invested in new equipment and technology and is now launching a matt uncoated magazine product. Its strategy formulation includes a statement that “wood-containing papers must be produced on a large scale in cost-effective plants of high technical status and high productivity. Production efficiency must be constantly improved in quest of improved profitability by tuning up production equipment, by measures to reduce costs, and by restructuring and investments.”
Sweden and the other Nordic countries are in a similar situation to Canada with an abundant availability of coniferous raw material suitable for virgin fibre-based mechanical papers, but with markets thousands of kilometres away. The Nordic suppliers have developed their business strategy accordingly.
Holmen Paper concentrates on mechanical printing papers, primarily on uncoated papers. It has traditionally been a large-scale supplier of good quality newsprint, which has been diversified to other mechanicals during the 1990s. Today, Holmen is the seventh largest newsprint supplier in the world. It has continuously invested in maintaining the technical competitiveness and efficiency of its production, as well as the product quality.
This active and aggressive investment strategy has yielded good results. Holmen’s profitability is among the highest in the global paper industry. During the last five years, the average operating margin has been 13.5%, and return on equity slightly more than that. Investments have varied around 10% of sales. Holmen Paper, the mechanical paper division of Holmen Corporation, contributed to more than half of the profits of the whole corporation in 1998-1999, although its sales were one third of the total. The other activities of Holmen include Iggesund Paperboard, Iggesund Timber and Holmen Forests
Holmen installed a 290 000-t/y high capacity newsprint line in its Braviken mill only five years ago. In 2002, it will start up another new machine of similar size, this time in Hallstavik. The efficiency of the company’s existing machinery has been improved by replacing the critical equipment such as wet end, press equipment and winders, for higher speeds and productivity. It has also worked towards enhancing the competitiveness of its products by improving the printability through better filler distribution, and through surface treatment by soft calendering.
Holmen has not installed coating equipment, but worked with “internal coating” for high brightness and opacity, as well as developed paper functionality in the colour printing through a uniform ink absorbency. It has constantly maintained the high bulk of its uncoated products.
Holmen’s Hallstavik mill has been among the leading newsprint producers since 1915.
The first three paper machines at Hallstavik started up between 1915 and 1920 when the mill was built. The mill was the largest newsprint paper mill in the world that time. It also had the world largest paper machines: two machines had a trim width of 4.5 m. These machines were running until the 1970s, when they were finally dismantled and replaced by PM 11 and PM 12.
Today, Holmen has four paper mills. The Hallstavik mill runs four paper machines. Braviken, 200 km south of Hallstavik, has three very modern and efficient machines. Vargn runs LWC and MWC grades on a medium-scale machine. The “baby” of the Holmen family is in Spain, Papelera Peninsular, purchased in 2000. It has one modern medium-sized DIP-based newsprint machine with surface sizing capabilities.
Holmen has a special expertise in TMP, which it produces in Hallstavik and in Braviken. The raw material know how has brought market strength, developing the good reputation of Holmen newsprint, which is known for its trouble-free printing performance and low number of press breaks
Holmen’s sheet is known for its strength and bulk. Its critical properties have been guaranteed by a proper amount of strong TMP fibres. The high brighness of TMP is achieved using new raw materials and a peroxide bleaching method. To adjust the production costs and maintain its attractiveness to the European urban printing houses, the furnish includes a sufficient amount of DIP.
Hallstavik has pioneered many technologies from its beginning. One recent example of that is the winding equipment: it installed the first WinBelt winder, on PM 2 in 1991. Since then, several other WinBelts have been installed on other lines in Hallsta mill to replace older, inefficient technologies. In 2001, a new soft calender — OptiSoft Slimline — is being built installed on PM 12.
PM 12 development
The evolution of Hallstavik’s PM 12 followed Holmen’s typical machinery development strategy. Two suppliers originally built the machine in 1974: Voith delivered the wet end and Valmet (now Metso Paper) the dry end. In 1992, Valmet was asked to install the SpeedFormer gap former with the headbox and PressRun blow boxes to increase the speed to 1200 m/min, as a way to improve the efficiency and to reduce the breaks. A WinBelt winder was installed as well to improve the winding efficiency and to produce large diameter rolls with no wrinkles.
Kjell Buhre, production manager of PM 12, described the machine performance. “The machine produces 210 000 t/y of standard newsprint at a usual running speed around 1200 m/min. PM 12’s wire width is 9.15 m and the trim is 8.6 m. We use 45% DIP, the rest is TMP. Most of the paper is 45 g/m2, but the trend is to 42 g/m2. We still produce traditional 49 g/m2 newsprint, 10% of production. Our strength is perhaps that our sheet is stronger and stiffer compared with the competition. Density on reel is 620 kg/cum. The 45-g paper has 63% brightness, 93% opacity. Bentsen roughness is 42 ml. Total efficiency of PM 12 is 84 to 87%.”
In 2001, Hallstavik will finalize a US$30 million investment project on PM 12. This project includes an OptiReel, distributed control system and a new soft calender — OptiSoft SlimLine — which is also a new product for the supplier, Metso Paper. Start-up is scheduled for November. This particular delivery happens to be Metso’s 100th softcalender. OptiSoft has an advantage of a wide nip loading range, which has been widened to the low end through gliding bearings. The SlimLine novelty has a compact construction suitable for rebuilding. Also, the roll change was improved from the previous standards. The SlimLine also features a modular and sturdy construction, and easy maintenance and operation.
Buhre believes that the soft calender is becoming standard equipment in newsprint production. “We have already had a soft calender in Hallstavik on PM 2. All of Braviken’s three machines have soft calenders.”
In Sweden, six of the country’s 15 newsprint machines have a soft calender. It is becoming vital for the newsprint suppliers to soft calender the product, because the customers prefer the product. Less printing ink is consumed due to lower ink absorbency. The printed image is more uniform because of the even surface density.
MF PM part of
Lars Erik Roos, mill manager of Hallsta, says that the continuous improvement is vital for the survival of the 675000-t/y mill. The mill has developed uncoated mechanical products and has already launched Holmen Ultra Bright papers: 75% brightness and 90% opacity at 55 g/m2. It is a bulky paper; density is 730 kg/cum. Its customers use it for magazine printing. Another grade has a basis weight of 65 gm2. It is being produced on PM 2, but similar high bright grades will be produced on the new PM 11.
“Our strategy is to be the quality leader in improved newsprint grades, although there is still good prospects for good quality standard newsprint, which we emphasize as our products as well. For supporting our standard newsprint products, we have invested
in quality and efficiency, like those high-speed gap formers and soft calendering. But we also believe that there are good prospects for high bright uncoated magazine grades other than SC. These have high print gloss without unnecessary high sheet gloss, and the sheet is naturally stiff and bright. The production costs of uncoated mechanical papers are competitive against the coated grades, and the performance of our special grades is very similar to those more expensive ones. Thus, we have invested in such a production at our coming PM 11.” The new machine will have an OptiLoad multi-nip calender and Winbelt winder.
Holmen’s Braviken Mill is one of the most advanced and efficient newsprint mills on the globe with production of 700 000 t/y on three machines and only 700 people. Its furnish consists of 250 000 t/y of DIP and 450 000 t/y of TMP, which is allocated over the three machines.
Airi Nikko, head of paper production at PM 51, has had experience with soft calendering since the start-up of the rebuilt machine in February 1998. PM 51 has an 8.8-m wide trim and runs at about 1350 m/min. It produces yellow, white and pink catalogue papers, basis weight ranging from 34 to 42 g/m2. PM 51’s production is about 180 000 t/y. In January 1999, Braviken installed another Metso soft calender, on PM 52. This machine produces 250 000 t/y of standard newsprint (42 to 45 g/m2) at a speed of 1500 m/min. PM 53 is its most recent newsprint machine running at 1700 m/min.
Braviken started soft calendered newsprint production in 1996, when PM 53 started up. Since then, the mill has been convinced that soft calendering is necessary for survival in newsprint markets. Braviken selected Metso calenders, because they offered additional flexibility and production security. “Downtimes are critical in newsprint production, as well as flexibility in adapting the running parameters. We already had a good experience with the Voith soft calender. We needed similar technology for the rest of the machines. Valmet offered a soft calender with new technology, the gliding bearings, which enable running at low nip loads as well. The usual soft calenders have a forbidden loading range at 60 to 90 kN/m2. While the Valmet price was also suitable, we selected them this time,” Nikko explained.
“The new calenders have offered us the expected additional flexibility. We can tailor the paper differently for cold set and heat set printing. Sym-Z rolls have a good CD-controlling efficiency, and they seem to be acceptable in respect to maintenance – oil leakage is not a problem at all. We have not lost in total efficiency compared to the times with hard calendering. The change interval of the soft rolls is three months. We have been able to change the rolls during the felt change, so it has not caused any reduction in capacity. Our bottleneck in calendering is not the soft calender, but the caliper measurements after the softcalender, which are not sufficiently reliable yet for the fine tuning of the sheet.
“Soft calender loading at newsprint is relatively low — we use loads ranging from 60 to 250 kN/m. Our roll surface temperatures are up to 120C. The density of the paper is 620 to 675 kg/m3. Speeds are high, but the load is not the critical factor in newsprint calendering. What Valmet has been able to offer us in calendering is a good service in quality development, as well as tools which give us flexibility to produce each customer the products they want,” Nikko concluded.
Hannu Oinonen is an independent researcher based in Helsinki, Finland: Hannu.Oinonen@clinet.fi
TABLE I. Production lines and machinery of Holmen Paper.
|Mill, machine||Start- up||Grades||Wire width||Speed||Capacity (t/y)||Soft calender|
|Hallstavik, PM 2||1958||Newsprint specialties||5750||850||105 000||1999|
|Hallstavik, PM 3||1963||SC-paper||7150||1000||140 000||Two supercalenders|
|Hallstavik, PM 11*||1967||Improved newsprint||9050||1150||220 000||Will install an|
|Hallstavik, PM 12||1974||Std newprint||9150||1200||210 000||2000|
|Braviken, PM 51||1977||Catalogue papers||9150||1350||180 000||1998|
|Braviken, PM 52||1985||Std newsprint||9150||1500||250 000||1999|
|Braviken, PM 53||1996||Std newsprint||9650||1800||290 000||1996|
|Vargn Bruk, PM 1||1961||LWC and MWC papers||5400||1000||120 000||Two supercalenders|
|Papelera Peninsular, Spain, PM 1||1998||Std. newsprint||6800||1350||200 000||1998|
|Total capacity of mechanical papers 1.7 million tonnes|
* PM 11 will be replaced by completely new MF-machine with a multi-nip calender in April 2002.