By Steve Cole, Director Global Product Management - Xerium Technologies, US
BRUSSELS,
Oct. 3, 2011
(RISI) -
Paper machines require hlgh amounts of energy to remove water in the papermaking process. New technologies and products have been recently introduced to reduce this energy consumption and create financial value for customers, both in roll and paper machine clothing products. Read Part I here.
Press section: PMC technology continued
Press clothing technology is a major influencing factor in the efficiency and energy consumption in the pressing process. Xerium has developed and introduced exclusive technology to specifically improve the effectiveness of dewatering and to improve sheet quality.
Case history #2
A tissue customer in Europe was also evaluating methods to reduce energy costs on its machine making toweling grades at over 1,500 m/min. Huyck.Wangner applications engineers recommended and applied the new Impact felt technology on the tissue pickup position. Impact incorporates a unique non-woven base and specially engineered batt technology which is ideal for machines requiring advanced drying performance and reduced energy consumption. The customer immediately experienced a 5% reduction in drying energy consumption and reordered additional Impact felts for the position.
Case history #3
A European customer, producing printing and writing grades on a tri-nip +4th press at 1,500 m/min wanted to optimize energy consumption in its press. When Huyck.Wangner became involved with the project, the customer was applying conventional laminated press fabrics and using a total of six uhle boxes across the various positions to condition and dewater the felts. Huyck.Wangner applications engineers recommended the new Exxact press fabric technology for all positions. Exxact felt technology provides an integrated triple layer structure with compressible base concept for maximum dewatering. Based on multi-shaft weaving looms with two different warp systems, Exxact is the world's first support shute binder (SSB) press fabric. SSB is the triple layer forming technology patented by Xerium known as Huytexx and Synergie. Exxact's patented concept provides high nip dewatering, fast start-up, uniform profiles and improved runnability.
Upon startup, the customer was able to reduce the size and number of vacuum pumps in the press resulting in over $500,000 in annual savings. The customer also reported over $350,000 in annualized savings in press drive load costs after reducing the vacuum, for a grand total of over $850,000 in savings per year.
Press section: rolls technology
Optimizing roll cover technology and press operational configuration can have significant impact on energy consumption on the paper machine. By properly applying cover materials, venting options, and proper hardness levels for ideal nip intensities, roll cover strategies can either help or hinder the papermaker's efforts to reduce energy costs.
Case history #1
A European customer, producing coated grades from 450-800 m/min wanted to increase dryness and improve sheet bulk, existing of 23.8%. Both press roll sections were 7 P&J and only grooved and the suction press roll was 10 P&J, suction, blind-drilled and grooved, with an open area of 40%. Stowe Woodward application engineers recommended that for press rolls in the 1st and 2nd nips, the mill change to Stowe Woodward Blue Steel 15 P&J blind-drilled and grooved at 38% open area. For the suction press roll a recommendation was applied for Stowe's Eclipse HP 15 P&J suction holes and blind-drilled and grooved with an open area of 45%.
At the same time, the customer changed from laminated press felts to Exxact technology for maximum dewatering. As a result of the press roll and felt optimization, the customer reported a dryness improvement of more than 2%, improved sheet bulk, and $820,000 in combined annualized energy savings from reduced steam and vacuum pump operations.
Case history #2
A customer utilizing two rubber roll covers in the suction pressure and blind-drilled press roll positions on a European tissue machine operating at 900 m/min engaged Stowe Woodward to help it discover ways to reduce energy costs and improve runnability. The goals of the project were: 1) improve nip dewatering at these positions, 2) eliminate the cover failures on the ends of the rubber covers that the mill had been experiencing, and, 3) eliminate the use of water cooling of the rubber cover in the press position.
Stowe Woodward engineers used Thermography and NipProfiler® measurements to evaluate the nip geometry before the polyurethane suction pressure roll and blind-drilled roll were installed. PressManager® studies were also done to evaluate theoretical dryness improvement potential. This program balances water flow in the nip and allows for the proper venting of the cover. Polyurethane covers are able to run with very high open area with additional grooves for better nip dewatering and higher transverse flow.
The NipProfiler® study performed on the suction pressure roll showed that the edges of the cover were overloaded. The edge relief was changed on the 25 P&J polyurethane cover to alleviate this problem. This Rebel cover has been running for almost one year with improved dewatering due to the grooving of the cover. As a result, the steam box has been removed from the roll.
The blind-drilled rubber cover had been water cooled with 16°C water to help control its temperature. This was causing bonding failures of the cover due to water migration. The recommendation was to use another Rebel 30 P&J polyurethane cover that was blind-drilled and grooved, without water cooling. This was possible because of the low hysteresis of Rebel's unique polyurethane compound. Thermography of this cover showed that it operates with a 50°C surface temperature, a full 5°C cooler than the rubber cover that was water cooled.
As a result of implementing Stowe Woodward's recommendations, the customer realized a steam reduction of one tonne/hr, or 10%, equaling a savings of $207,000/yr, and the ability to turn off water cooling on the blind-drilled pressure roll saved $55,200/yr. The mill has also observed less vibration on the paper machine and a more uniform moisture profile.
Case history #3
A bleached board customer was striving to maintain a minimum caliper at a designated sheet smoothness level. Pressing the sheet too hard reduces the caliper and therefore decreases the smoothness by marking the sheet with the felt. In order to obtain the required smoothness, the sheet must be calendered, but calendering the sheet also creates a denser sheet and resulting thinner caliper. The second function of the calender stack is to build a uniform reel, requiring the cross machine sheet caliper to be uniform. Historically, to ensure that the minimum caliper was achieved, the customer was required to add basis weight - so more fiber was added. The sheet was then heavier than it needed to be; consequently, more energy was required to dry the heavier sheet.
After consulting with Stowe Woodward application engineers, the customer installed two patented SMART® Rolls, which measure nip pressures in real-time, to analyze and optimize the moisture removal in the press section. After the SMART Rolls were installed, the customer was able to tune each nip thereby generating a more uniform, less dense, and higher caliper sheet of paper exiting the press section. The uniform caliper exiting the press section reduced the calendering required to build the reel, and eliminated the need to reduce the sheet caliper. The greater sheet caliper required less fiber to manufacture the same sheet of paper. Less fiber to manufacture the sheet produced a lighter weight sheet which required less energy for drying.
Not only was energy reduced by drying a lighter sheet, there was less energy used to produce the smaller amount of fiber in the sheet. Combining the energy and fiber savings, the customer saved over $700,000/yr.
Conclusion
As customers continually look for more ways to reduce total costs-per-ton, Xerium research and development efforts will increasingly focus on unique products and materials to support these efforts.
Energy savings is only one of the major cost drivers ValueResults has affected. Customers continue to report significant savings in fiber and chemical usage while numerous customers are realizing new levels of speed, production, and overall productivity and efficiency. The benefits are greatly enhanced with a combined application strategy of both PMC and roll technology.
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