PPI Awards 2011: Honors well earned www.risi.com - December 2011
By BRIAN DUFFY and BRAD BENZ Nalco technology helped a linerboard mill improve strength and increase machine speed while reducing basis weight and steam use ACHIEVING STRENGTH AND PRODUCTIVITY In recent years, containerboard demand has been rebounding in the worldwide economic recovery and globalization of the market. Faster machine speeds, increased operating rates, and the demand for fiber to fulfill production capacity needs has been an ongoing challenge to the industry. This demand has caused fiber prices to escalate, especially recycled fiber such as OCC from recovery processes. Many producers are implementing plans around fiber reduction as it directly relates to manufacturing cost and selling prices. Additionally, management teams are discussing this every day in their plants. Having a well-managed chemical program and a well-run mechanical operation is a highly important and effective way to sustain the process of fiber reduction without compromising strength such as ECT or compression strength. Moving to lighter weights, strength, and energy Table 1 - BASIS WEIGHTS FOR KEY LINERBOARD GRADES (SOURCE: RISI INTERNATIONAL, 2007) costs are critical drivers in the board and packaging market. However, achieving the desired end-product performance to satisfy demand while maintaining and improving production efficiency can be a difficult task. THE LIGHT-WEIGHTING OF CONTAINERBOARD The shift to lighter basis weights for containerboard has been a compelling industry trend for the last 20 years. Since the adoption of Alternate Rule 41 in 1990, many users have opted for box compression standards as the preferred method for specifying their boxes. Several factors have significantly influenced this shift, including advances in manufacturing technology, shifts in fiber supply, supply chain considerations and sustainability awareness. Over time, basis weights have also been steadily declining for key linerboard grades, as illustrated in Table 1. Achieving strength and reduced basis weight targets can be a challenge for any papermaker, especially when lower quality fibers are part of the furnish mix. Use of Nalco s patented METRIX technology program allows paperboard manufacturers to increase strength, lower basis weight, enhance production and improve sheet quality. Variability in quality and supply of raw materials also presents significant challenges to paperboard manufacturers. Increasing refining to achieve strength often leads to reduced drainage, lower retention and higher energy costs. Increasing starch dosages may also be ineffective as fibers become saturated and additional starch cannot be retained. Overuse of other cationic additives such as alum and coagulants may also cause the furnish to become cationically dispersed, affecting retention, sizing, system Pulp & Paper International (PPI) December 2011
chemicals foam, and finished product quality. Nalco developed the multi-component METRIX retention, drainage, and pressability program to allow board manufacturers to simultaneously optimize basis weight, strength, caliper and sheet smoothness. For example, the METRIX technology program provides papermakers with the flexibility to increase strength, while at the same time reducing basis weight, increasing machine speed, improving sheet properties and lowering fiber and energy costs. Over the past 10 years, Nalco has committed significant time and research investment into the continued development of METRIX technology. Currently, the 7th generation of this technology is being marketed, and the 8th generation will be available globally in late 2012. CASE STUDY EXAMPLE Mill Overview Grade: Linerboard Basis weight produced: 35 and 42#/1000ft 2 (170 and 205 g/m 2 ) Machine type: Single ply fourdrinier Press type: 1st Straight through, 2nd LNP Production rate: 45 tons/hr Machine speed: 1,700-2,250 ft/min (518-686 m/min) Furnish: 65% OCC and 35% kraft Wet-end chemistry: CAT PAM flocculant, thin & thick stock starch, rosin size & alum ph: Acid A linerboard manufacturer capable of producing 1,200 tons/day (1,091 tonnes/day) realized serial reductions in production. Most days averaged 1,030 tons (938 tonnes) which was due to a need for higher basis weight to meet quality specifications. Low production was most prevalent on 35# (170 g/ m 2 ) high performance linerboard and 42# (205 g/m 2 ) linerboard. This integrated board mill was using a higher percentage of recycle fiber in comparison with unbleached kraft pulp, 65% and 35% respectively. Recycled fiber quality had also suffered over the years. The thick stock Canadian standard freeness of recycled fiber had declined by 100 ml or greater from the facility s recycle plant. Lower freeness was making it increasingly difficult to achieve sheet quality parameters at nominal basis weight and target speed/produc- Fig. 1 - METRIX TECHNOLOGY RESULTS 35# HIGH PERFORMANCE LINERBOARD December 2011 Pulp & Paper International (PPI)
chemicals tion. On occasion, the paper machine in question was running at target speed, but rarely longer than one day. Several mechanical changes (refining, fourdrinier setup, pressing, drying) contributed to minimal improvements in strength and speed. In addition, several wet end chemical trials (coagulant, flocculant, starch, silica, strength resin) achieved minimal to moderate benefit in quality parameters. To meet quality goals, the mill was forced to run 2-3 lb (0.9-1.4 kg) over standard basis weight on select grades for this paper machine. This manufacturer sold finished board on a manufactured square foot/meter basis. Therefore, running over target created several drawbacks which included increased fiber cost, slower machine speed, decreased production rates, and higher energy and unit cost per ton of linerboard produced. The manufacturer wanted to run the machine at nominal basis weight or below while maintaining strength targets in ring crush and mullen. In addition, other key business drivers were increased production rates and reduced operating costs. Nalco understood that meeting these goals could prove difficult given the present and past operating conditions on the paper machine and that minimal impacts had been realized with previous changes. Nalco s Industry Technical Consultants in cooperation with its on-site team performed a thorough mechanical, operational and chemical (MOC) audit. The team provided several recommendations in each area with a major focus on chemistry. From a chemistry standpoint, there was a need to address drainage on the fourdrinier without disrupting sheet formation. This particular machine has a very long forming section. The wet end chemistry and their injection point was not overly complex with the use of alum, starch, rosin size and cationic flocculant. A review of audit findings was communicated to the manufacturer and a plan was proposed to improve machine speed and increase strength. Chemical recommendations were made to limit early fourdrinier drainage, focusing on vacuum drainage and pressing, as well as strength development. PROGRAM DESIGN As a first step, a high molecular weight cationic floc- Fig. 2 - METRIX TECHNOLOGY RESULTS 42# LINERBOARD Pulp & Paper International (PPI) December 2011
chemicals culant along with colloidal silica and a balance of thin versus thick stock starch provided necessary drainage on the fourdrinier. The ability to move the dry line on the fourdrinier was evident. However, this particular chemical program did not result in increased machine speed or strength. Several parameters were adjusted on the fourdrinier and press section to take advantage of the drainage, but no adjustment provided sustained results. This was not a major setback as pre-trial audit findings suggested this was possibly due to water handling in the press section. The initial chemical program provided important technical information and demonstrated that the Nalco team had the ability to understand the papermaking process dynamics and provide a technical reason for the paper machine response observed as well as propose a solution. The next step focused on a two-component polymer approach using a high molecular weight cationic flocculant in combination with a METRIX technology product. The technology was selected for this customer due to proven effectiveness with similar furnishes and also due to the inability of a traditional retention and drainage program to meet the mill s key business drivers. In addition, METRIX technology provides additional strength to allow for reduction in basis weight and refining. Experience with the technology, along with a thorough understanding of the papermaking process at this manufacturer s facility, allowed Nalco to design a program that would provide maximum environmental and financial savings at the lowest sustainable cost. This program integration provides the customer an Environmental Return on Investment (eroi), delivering both environmental performance and financial payback. In designing the feed strategy of step two, existing wet end additives were considered as well as their respective location to each unit operation. A feed location was selected that provided maximum retention with minimal interference from disruptive fines and colloidal material. The strategy incorporated a co-mix approach with high molecular weight cationic flocculant and METRIX technology. At this facility an overfeed situation occurred at 3.0 lb/ton (1.36 kg/ton) of METRIX technology; therefore, the team selected 2.0 lb/ton (0.91 kg/ton) as the final dosage. PROGRAM RESULTS Analysis was completed on 35# and 42# grades, running the paper machine at maximum steam consumption/speed optimization. 4-5% basis weight reduction 7-10% manufactured square footage increase 7-10% reel speed increase 1.5-2 ton per hour production increase 6% reduction in refining energy per unit ton on 42# (205 g/m 2 ), no change on 35# (170 g/m 2 ) Maintained target ring crush and mullen Optimum METRIX technology dosage 2 to 2.5 lb/ ton (0.91 to 1.13 kg/ton) Minimal dosage changes for existing wet end chemistry Customer ROI: $750/operating hour Saved 90,000 gallons/yr in flocculant makedown water The METRIX Technology response prior to a speed and basis weight change showed a 14% reduction in steam consumption and a 10% increase in both ring crush and mullen, grade dependent. CONCLUSION METRIX technology is a synergistic, multi-component program developed to enhance productivity, press section dewatering and strength development for paperboard manufacturers. It encompasses the use of a reactive polymer and one of Nalco s advanced retention and drainage programs. Program benefits are designed to include increased sheet strength and machine speed from enhanced dewatering during pressing and drying operations. PPI Brian Duffy is Senior Industry Development Manager, Board & Packaging Grades, and Brad Benz, Senior Industry Technical Consultant, Nalco Company Literature 1. The Future of Lightweight Containerboard in North America, RISI International, 2007 2. Corrugated Today Magazine, July/August 2011 To read more articles on Chemicals, visit our Chemicals Technology Channel at www.risi.com/ technologychannels/chemicals Reprinted with permission from Pulp & Paper International December 2011
Nalco Your partner for sustainable growth Cost reduction is a key business driver for every papermaker. Nalco solutions are specially designed to deliver cost improvement, while reducing environmental impact. Value delivered Water reuse GRADE: uncoated fine paper APPLICATION: PARETO increased production by reducing wet-end breaks reduced fresh water usage: 105,000 m 3 /year estimated annual savings: US$3,400,000 Water usage System closure Shower optimization Additive dilution Water management Steam savings GRADE: coated fine paper APPLICATION: VELOX increased machine speed from 1,150 to 1,200 m/min estimated annual savings: US$1,500,000 Energy savings Felt performance Press dewatering Boiler efficiency Water & energy savings GRADE: board APPLICATION: 3D TRASAR technology real-time monitoring and control reduced acid cleaning frequency by 50% eliminated unscheduled shutdown estimated annual savings: US$30,000 Nalco s key solutions PARETO mixing technology NAL-TEX advanced cleaning 3D TRASAR technology for cooling and boiler water VELOX press dewatering Integrated Water Management (IWM) Waste water recycle GRADE: gypsum liner APPLICATION: Waste Water Treatment improved end product quality by eliminating chlorine ions from waste stream enabled 16,000 m 3 per day of waste water to be recycled to papermaking process Nalco is your partner in achieving your economic, environmental and social goals. Nalco Company 1601 West Diehl Road Naperville, Illinois 60563-1198 USA 630 305 1000 Latin America: Av. das Nações Unidas 17.891 6 Andar 04795-100 São Paulo SP Brazil 55 11 5644 6500 Europe: A-One Business Center Z.A. La Pièce 1 Route de l Etraz 1180-Rolle Switzerland 41 (0)21 614 6400 Asia Pacific: 2 International Business Park #02-20 The Strategy Tower 2 Singapore 609930 65 6505 6868 www.nalco.com/paper
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