SPCI´99: Sunds session targets fiberline efficiency
Incremental increases in quality and decreases in costs can mean the difference between success and failure at pulp and paper mills around the world. With that in mind, Sunds Defibrator focused on "Boosting Efficiency in Fiberline Technology" at its 13th Annual International Technical Seminar at the Grand Hotel Saltsjsbaden in Stockholm, May 30th and 31st.Lars NSsman, CEO of Sunds Defibrator, welcomed the audience, which included about 125 attendees from pulp and paper companies, the trade press, and Sunds. Lars-*ke Lindstrsm, Senior Vice President of Research and Development for Sunds Defibrator, introduced the seminar program and served as moderator throughout the session.The world of woodhandlingPasi MSkelS, Sales Manager for Sunds Defibrator Woodhandling Oy, Finland, spoke on developments in Sunds' wood handling technology. He noted that the company's GentleFeed wood handling system, which processes logs more gently than traditional technology, produces lower wood losses, better chip quality and high availability. The system, composed of a series of moving plates, also offers lower maintenance costs and less noise than traditional systems. According to MSkelS, the system produces 2% to 3.5% lower wood losses. On an annual basis at a large pulp mill, this would translate to one million cubic meters of wood, meaning that the system could pay for itself in one year. GentleFeed Drum infeed systems are in use at Advance Agro, Thailand, and MetsS-Rauma AB, among other installations. Another new Sunds development, a log pretreatment system for stringy bark wood species such as eucalyptus, can also cut wood losses. The equipment cuts barks into shorter pieces so they don't produce large bundles of bark that get into the chipper. With less bark going into the chipper, the system can produce cleaner chips and lower wood losses. Also, the more reliable bark removal system can produce higher uptime. The first such system will be installed in Indonesia later this year.MSkelS also noted that Sunds' state of the art Camura GS Chipper can produce homogeneous chip quality and minimum pins and fines generation. The chipper produces fewer overthick chips (5% of total compared with 10% in conventional systems). A better way to wash?Gunnar Carr* of Sunds Defibrator addressed the topic of "What's So Special About Press Washing?" Carr* examined using press washing in the bleach plant compared with displacement washing. He noted that both systems operate at about 90 plus percent efficiency. However, under upset conditions, displacement washer efficiency drops dramatically, while the press washing system efficiency drops much less. He noted that Advance Agro in Thailand was the first press-based fiberline. Monica Bokstrsm of Sunds Defibrator continued on this theme by describing the operating experience at Advance Agro, which started up in January 1996. The mill uses five Super Batch digesters for cooking and its bleach plant is designed to produce either ECF or TCF pulp, using oxygen delignification. Within a year, the fiberline reached 100% of capacity, producing well above 600 tons per day (tpd), sometimes 660 to 680 tpd. One of the mill's challenges is to deal with density variations in wood and rapid changes in wood chemical composition, which can produce differences in yield and brightness after cooking.According to Bokstrsm, the press washer system features low water consumption and low effluent volumes. Within the press washing system it is easy to control pH, temperature and pulp consistency between the stages. The washers also feature low carryover and have low heat and cooling requirements. As a result, Advance Agro is better able to handle wood quality.Hardwood trendsSome pulp and paper mills are considering using more hardwood pulp in order to improve their end products. Ingrid Englund of Stora Enso Research examined some of the important properties of hardwood fiber in paper and board products. She noted that there is great potential to improve the properties of graphic paper and paperboard using acacia, birch and eucalyptus pulp."In fine paper, the driving force is the concept of using only hardwood pulp in certain grades," said Englund. In whitetop linerboard, the idea is to use hardwood pulp for the surface layer, which can be considered a fine paper due to its printability.She noted that eucalyptus and birch pulps are both popular while interest in acacia is growing. Of these fibers, birch is the longest, at about 1 mm, with eucalyptus being shorter, at 0.9 mm, and acacia at 0.7 mm. The varying lengths and widths of these fibers produce different pulp properties. For example, acacia and eucalyptus pulps rank higher on whiteness, opacity and formation, while birch pulp is stronger and eucalyptus has better bulk. Englund also noted that genetic research is dramatically improving growing rates for certain hardwoods. For example, a breeding program at Stora Enso Celbi in Portugal involving Iberian E. Globulus eucalyptus pulp produced a 70% gain in tons of bleached pulp per hectare per year, substantially reducing wood costs. The return on investment in genetics research in this example was 31%, she said. More fine paper trendsThe goals that papermakers want to achieve with their machines are changing, and paper machinery technology is keeping pace with those new goals. That was the message of a presentation by Markku Karlsson of Valmet Corp., who focused his presentation on fine paper production.The changes in fine paper production are being driven by changes in printing technology. Conventional "impact" printing, such as letterset, lithography and gravure, is being displaced by "non-impact" printing such as electrography (laser printing) and ink jet printers.For example, office business papers (typically woodfree cut size paper) to be used in non-impact printers must have good bulk and thermal stability. Karlsson noted that pulping processes and paper machine processes both contribute to improving these properties.He suggested that, to produce paper with low curl and high tensile strength, papermakers should look to changes in the paper machine. These qualities can be improved with a fully supported web, closed transfer in the press section, the use of shoe presses and no open draws, and higher dryness after the press. "Without these features, we are excessively losing bulk and producing internal stresses in the fiber that can increase the tendency of the paper to curl," he said. Other ways to develop higher bulk include increasing filler content and using more refining, multilayering, impingement drying, shoe pressing and calendering.Award winnerAt the conclusion of the Seminar, Lars Näsman presented the company's internal 1998 Product Excellence Award to Arvo Jonka, R&D Manager, Woodhanding Division, for the invention and development Sunds' GentleFeed woodhandling system. The internal competition recognizes Sunds products that are commercially accepted and successful in the marketplace.(Papernews) Alan Rooks