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IMPC CONFERENCE COVERAGE: the next step is needed

Over the years, certain topics have dominated research in the field of mechanical pulping. In his welcoming remarks to delegates attending the 22nd International Mechanical Pulping Conference (IMPC), ...

September 1, 2001
By Pulp & Paper Canada


Over the years, certain topics have dominated research in the field of mechanical pulping. In his welcoming remarks to delegates attending the 22nd International Mechanical Pulping Conference (IMPC), held in Helsinki in June, conference chairman Erkki Peltonen said that pulp fractionation, pulp screening, pulp quality optimization and process control have been in the forefront in recent years.

Rising oil prices put upward pressure on energy prices and, for an energy-intensive process such as mechanical pulping, there is increased pressure to find energy-saving solutions. “Recent innovations have taken us a step nearer to the goal, although it has still not been reached,” Peltonen said.

The opening session featured three keynote papers. The first was by Jasper Scott, IPC Magazines, Britain’s largest publisher of consumer magazines — 92, split into five groups. His talk was titled Tailoring pulps to the changing needs of customers. Scott called IPC a “brand-centric, media-neutral company”. That is, it no longer focuses on just publishing magazines although that remains its core business. Its electronic publishing end is growing.


The company expects to use 107 000 tonnes of paper in 2001, of which 40 000 tonnes is LWC. The main challenge the company faces is increased competition from a number of sources, affecting circulation and advertising revenue. “We need more efficient and cost-effective manufacturing to stay competitive and profitable.” Sound familiar?

What does Scott’s company, and the industry, need? “More quality and service, for less. We need lighter-weight papers with better gloss, opacity, runnability and rigidity.”

How can pulp makers help IPC? Scott gave the example of What’s on TV, a weekly television guide published in England. It is IPC’s biggest circulation title, two million per week. In a “cutthroat market”, it needs to look good and be economical. To publish it, IPC uses 18 000 tonnes per year (t/y) of SC offset uncoated paper.

IPC’s problem is excessive ink costs due to the absorption of SC uncoated paper. This costs IPC more than one million Euros per year than if it were to use LWC. To use LWC would cost IPC more overall. Therefore, Scott asked, can the pulp in SC offset be tailored to use less ink? Is there too much independent development work in the pulp and paper, ink and press industry, he added? “For every action, there is a reaction. We should try to work together more and think about the whole product, from pulp to printed product.”

A mill perspective was given by Eeva Jermstrom, UPM-Kymmene, who also discussed changes in customer expectations. The communications industry is under increasing pressure from the electronic media. To meet the competition, there is a greater need for “tailored” products. This means there is a need for new coated and uncoated paper grades.

Future requirements for printing papers will be good runnability, cost efficiency and no mechanical faults. The challenge to the industry is to combine the needs of increased targetting and personalization in the media with increased competition while achieving efficient production.

Antti Arjas, KCL (Finnish Pulp and Paper Research Institute) explained how mechanical pulps used to be seen as a cheap substitute for chemical pulp. Now, they are a key component of many paper grades. They are valuable in applications where good printing properties — opacity, sufficient bulk/stiffness — are needed.

Combining various properties of mechanical pulps is not enough, Arjas added. The industry needs to develop them further but: “We need to know what we want.”

Pulp made of “tailored” fractions is more favourable than pulp “as it comes”. Thus, the properties of the individual fractions need to be determined so that every fraction serves a purpose.

Different fractions have different tasks. Long fibres contribute to formation and strength. Fines produce an even surface. However, different fractions can also have negative effects. The entire optimization process is a very complex compromise that should be based on the concept of the “critical property pairs”. That is, the net of functional properties whereby improving one or some of them leads to a deterioration of some others.

Nature has a 400-year head start

Session II dealt with fibre properties. The keynote speaker was Stuart Corson, PAPRO, New Zealand. He may have set a record for title length — Fibre: Redefining the boundaries or Nature is 400 million years ahead of us — Let’s work with her, not against her. The essence of mechanical pulping is the conversion of stiff wood fibres to flexible, bondable papermaking fibres. However, mechanical pulping technology is mature and not progressing. It hasn’t changed significantly in 150 years, Corson said. It’s time to look for new opportunities. Nature is 400 years ahead in the evolution of fibre.

Corson described a tree as an engineered structure; its fibres carry the trunk weight, dampen vibrational energy and transmit water up the trunk. Fibre has evolved to resist fatigue failure and internal collapse.

Microfibril alignment is the key factor in fibre strength. Microfibril angle is likely to significantly influence fibre collapse and refining energy demand. Mechanical pulping advances will be achieved through a fibre perspective for paper manufacturing, Corson said.

Mechanical pulping succeeds by exceeding the design limits of the fibre. Wouldn’t it be easier, Corson asked, to lower these limits? It is time to stop operating mechanical pulping as a crushing process and optimize it for the individual fibre’s needs.

The papermaking character development of the individual fibres can be audited to precisely measure and improve process efficiency. A fibre and paper quality audit links energy demand and process effects to wood and pulp fibre quality and paper and printability properties.

Fibre supply management is another opportunity. There is a need to minimize wood quality variations. Biofibre engineering is yet another opportunity for the industry. Select from one species a preferred group of trees with optimal fibres for papermaking.

Aspen’s path

In the session of Wood and fibre treatments, a presentation by Thomas Granfeldt, Metso Paper, and Rick Denton, Slave Lake Pulp, looked at aspen CTMP and the directions it is taking. In Canada, the trend in existing aspen mills is to increase bulk and brightness. To maximize bulk, the alkali charge in the impregnation stage must be minimized. Aspen has a high initial brightness and it can easily be bleached to 80+ levels. The most efficient way to bleach aspen CTMP is with hydrogen peroxide. To fully utilize the peroxide and reach as high a brightness as possible, a sufficient amount of alkali is essential for the bleaching stages.

Denton, production and technical manager at Slave Lake, then took the podium. Since the mill start-up in 1991, there has been a trend toward increasing the amount of high-bulk, high-brightness CTMP grades, used for paper. It is no longer just a replacement for hardwood kraft. In 1992, of 110 000 tonnes of pulp, 30 000 tonnes were high-bulk grades. In 2000, of 195 000 tonnes produced, 117 000 tonnes were high-bulk.

Denton thinks that in 2001, 85% of demand will be for high-bulk pulp. This trend should continue until all production is high-bulk grades.

High-bulk pulps must also have high brightness, low shive content and good cleanliness. The physical properties of the pulp must be suitable for paper machine runnability, but it should be noted that the bulk is the factor that controls other physical properties of aspen CTMP.

The keys to high-bulk, high-brightness CTMP are to refine as little as possible to the highest freeness acceptable and to minimize the use of chemicals that influence bulk properties.

Denton also spoke of reductive bleaching, a method to increase brightness without adding alkali and thus affecting bulk. There are various ways to do this.

Chip treatment — sulphite impregnation;

Addition of reducing agents — sulphite or hydrosulphite — into the refiner;

Reductive bleaching between
peroxide stages: the PRP process;

Reductive bleaching after the final peroxide bleaching stage: post-bleaching.

In Session 5, Measurement and control, William Strand, Pacific Simulation, was the invited speaker, talked about control development. In the 21st Century, mills must reduce operating costs. Low-cost production will be needed for long-term viability. Improved paper quality and reduced variability will be the keys to maintaining high-margin customers.

The goals of advanced controls will be the achievement of quantifiable economic benefits. These benefits include lower variable costs, lower fixed costs and improved quality.

Strand noted that the economics of advanced control are like any capital project. The yearly benefits fall over time while the annual costs rise. Advanced control projects present an opportunity for a very high return on investment. Therefore, Strand asked, why do so few refiners have advanced controls? Because, he answered, achieved benefits have not been sustained over time. Also, the systems have not met performance expectations and have often come in over budget. He estimated that 90% of advanced control systems are deactivated within one year.

Why is there such a low success rate in the pulp and paper industry while other industries are successful? Some of the reasons claimed for the industry’s low success rate are raw material variability, lack of online measurements and reduced technical staffs. Strand said that the industry does not recognize that advanced control and continuous performance improvement are the same process. Optimization should be looked at as a process not a project.

To implement control technology successfully, many steps are necessary: operator training, constant (24 x 7) support, system troubleshooting, performance tracking. Therefore, mills need to improve the underlying infrastructure. The benefits must be quantified. There has to be constant enhancement so that the goals of a control system match those of the mill. Support and maintenance are critical. Strand said that annual support and maintenance costs are about 15 to 20% of the initial implementation cost.

During each IMPC, the Arne Asplund Mechanical Pulping Award is presented for outstanding achievement in the research and development of mechanical pulping technology. In 2001, the award — sponsored by Metso Paper — was presented to Jan Sundholm, Finnish Pulp and Paper Research Institute (KCL). Sundholm studied early various means to reduce energy use in refiner mechanical pulping. Sundholm has also contributed to the understanding of the importance of fibre characteristics for the properties of high-quality SC and LWC papers made with TMP.

Helsinki was the centre of the pulp and paper world in June. Besides the IMPC, the city also hosted the Ecopapertech Conference and the PulPaper equipment exhibit. These three events were held in the Helsinki Fair Centre. Nearby, at the same time, the city also hosted the 8th International Conference on Biotechnology in the Pulp and Paper Industry.

The 2003 IMPC will be held in Quebec City, QC, and will be chaired by Dave McDonald, Paprican.

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