Seeking breakthrough technology in fiber use: significantly reduced manufacturing costs are possible if we rethink the process of fiber liberation.

Editor's note: This article is part of a continuing series of reports from the Forest, Wood and Paper Industry Technology Summit, held in May 2001 in Peachtree City, Georgia, USA. The Technology Summit was sponsored by TAPPI, AF&PA, and the U.S. Department of Energy's Office of Industrial Technology.

IN THIS ARTICLE, YOU WILL LEARN:

* The critical limitations or current pulping processes

* The technology gaps that must be bridged far the industry's continued viability.

* Project concepts--such as single-stage bleaching--that address these gaps.

The pulp and paper industry has always pursued simplified processes and reductions in capital intensity and operating costs. To maintain the vitality of the industry, we must continue to develop and deploy new technologies at a rapid pace.

Our industry's vision for fine manufacture of paper, pulp and forest products is to slash the cost of manufacturing by as much as 50%. The delignification process will be much more selective, operations will be simpler and more will be done with much less equipment. Specific objectives are likely to center on:

* Dramatic improvements in fiber value, cost, and use

* Simplification of the process

* Chemical use and cost

* Improved throughput.

SUMMIT MEETING

Industry experts gathered to discuss pulp processing challenge during the Technology Summit at Peachtree City in May 2001. To reset everyone's viewpoint, we spoke in terms of "fiber liberation" instead of terms like "pulping." Our mission was to map a research path to be followed under the Agenda 2020 program of AF&PA, TAPPI, and The U.S. Department of Energy's Office of Industrial Technology.

Participants all agreed that several gaps exist between today's technology and the technology needed to achieve the industry's vision. The current pulping process is too:

* non-selective and slow

* costly

* capital intensive and complicated

Although these gaps exist in the real world, some technologies are already being developed that could significantly change the rules of the game. For example, developments in bioprocessing and highly selective chemistries offer the promise of much more selective, economic access to papermaking fibers. However, while we need continued developments in these technologies, we also need to develop several enabling technologies. For example, we need dramatically simplified chemical recovery systems, and faster, less complicated fiber liberation unit operations.

BOLD TECHNOLOGICAL DEVELOPMENT AND USE

Most changes to the major pulping and recovery processes have been evolutionary. Yet, for the pulp and paper industry to move forward in terms of energy-efficiency, environmental performance, global competitiveness, and profitability, evolutionary progression does not seem fast enough. Recent research funding has yielded some very good incremental developments and some new ideas; but much more is needed. Technological breakthroughs--and deployment leading to sustainable profitability for both suppliers and customers--are overdue and necessary.

For our industry, new developments take time to implement, achieve commercial acceptance, and achieve wide distribution. The Summit Panel recognized the need for a much more streamlined process. One speed bump in the process is in the treatment of intellectual property. When a discovery is made, everything comes to a screeching halt while the system attempts to deal with the valuable new nugget of an idea. Intellectual momentum is lost while the process grinds on in a series of steps that can take years. By then, researchers, technologists, and application specialists may have grown frustrated, moved on, or given up.

One very effective way to manage access to intellectual property (IP) is through the use of a partnership called a consortium. In the consortium, all process and legal instruments needed to manage the IP are put in place ahead of their discovery, in a way that facilitates progress rather than blocks it.

THE GAPS: A CLOSER LOOK

Gap 1--The process is nonselective and slow: The current pulping process is both complicated and capital-intensive. Many process steps, using a number of different process chemicals, are required to liberate the fiber so that it is suitable for papermaking. For the most part, the only major components of the wood that form marketable products are the cellulose (in the form of papermaking fiber) and the extractives (in the form of tall oil for kraft pulping only). The remaining components are burned for energy (in the case of kraft pulping); left in the product, where it degrades the product's papermaking performance (in the case of mechanical pulping); or from a byproduct that requires additional processing or disposal. The current system is also indiscriminate and slow, and causes degradation of the higher value components. In general, fiber liberation is very expensive.

The industry needs fundamental breakthroughs in the development of highly selective and rapid separation processes for the major wood components. This would allow mills to redirect each component to its highest value use.

Gap 2--The process is costly: Process cost is closely linked with the other gaps, such as capital intensity; but in general the industry is not extracting the maximum value from available raw materials. A more selective liberation process will certainly help, but another example is in the area of biomass gasification.

Gasification of biomass is not yet cost-competitive with electricity generated by fossil fuels. One major goal of a biomass project would be to generate power in an integrated gasifier and combined cycle (IGCC) system plant. This uses the "waste" heat generated by the gasifier to produce electricity in a gas turbine. The efficiency of an IGCC plant would be more than 40%, compared to 25% for a direct-steam plant alone. However; IGGC technology is not yet commercially available.

Gap 3--The process is capital intensive and complicated: A modern chemical pulp mill cannot exist without systems for cooking, washing, recovering, and re-using chemicals. TO attain economies of scale, these systems have grown larger and larger; yet productivity gains have come at the expense of increased capital intensity.

The group agreed that capital intensity and complexity could be reduced in a number of ways. Two examples include:

1. Simplify the process by doing more with each operational unit. A good example of this approach would be a single stage bleaching or single stage washing operation.

2. Eliminate process steps. For example, the lime kiln operation might be eliminated by taking steps to produce lime directly in the recovery boiler.

PROJECT CONCEPTS FOR CLOSING THE GAPS

Selectivity--biopulping is one example of a highly selective approach to delignification. The process of pretreating wood chips with wood-decay fungi prior to pulping has already made good progress. Biopulping treatment of the wood chips reduces the amount of electrical energy needed for mechanical pulping.

For chemical pulping, biopulping has already been shown to reduce the viscosity losses in the cellulose while reducing the lignin content in the wood. Research has also shown that biopulping increases the accessibility of the hemicellulose for extraction.

The biopulping treatment is currently a two-week process done in storage piles or storage silos in a pulp mill wood yard. As the chips go into the pile, the fungus and a nutrient are applied and the temperature is maintained to optimize fungal growth. After two weeks, the chips are ready for pulping and, in the case of mechanical pulping, electrical energy use is reduced by 30%. Longer treatment times increase the benefits for both mechanical and chemical pulping.

The industry has much more to accomplish in the field of improved selectivity.

Capital intensity and complexity--The industry must address the capital intensity and complexity of its pulp mills. The development of a compact, integrated recovery process is just one example. Such a model would reduce the capital costs of the equipment required for chemical recovery and energy production, while ensuring cleaner air and cleaner water from the pulp mill. The gap filling technologies are design modifications to the existing, proven technology for recovery boilers. The design would also depend upon the availability of 90% + dry solids content black liquor, which would have a much higher heat value as fuel than conventional black liquor.

The basic technologies exist today. By modifying existing technologies to: 1) raise the dry solids content of black liquor, 2) properly introduce the calcium carbonate into the recovery boiler, and 3) complete the conversion of the chemicals after combustion in the recovery boiler, mills should be able to eliminate the lime kiln. If accomplished, this concept would yield the following benefits:

* 30% reduction in the capital cost of the chemical recovery boiler

* Elimination of the lime reburning kiln (capital and operating cost reduction)

* Increased evaporation of black liquor to the 90% + level of dry solids content

* Gasification of biomass "waste" for energy production

A BLEACH PLANT EXAMPLE

Modern bleach plants are complex. A single bleaching stage would represent a breakthrough compared to the present five-stage bleach plant with five washers, five washer seal tanks, five towers, five medium-consistency stock pumps, five steam mixers, and at least 10 filtrate pumps. Also, the total residence time of the pulp in the single stage bleach plant may be closer to 10 minutes--a fraction of the residence time (up to 10 hours) needed in current bleach plants.

The key reason that bleach plants rely on several stages is that no single chemical can presently remove all the residual lignin while preserving the strength of the cellulose in the pulp in a single batch treatment within reasonable time. The single stage concept involves a moving pulp mat, where the different bleach chemicals (mainly Cl[O.sup.2] and NaOH) move sequentially in pure plug flow through the mat. The single stage bleach plant may resemble a belt washer or a drum displacement washer with multiple wash zones, or another continuous multiple cross flow technology that is fed with several different bleaching chemicals.

To optimize the water balance and reduce the quantity of bleach plant filtrate, the chemicals would be added at a much higher concentration than currently used for conventional bleaching. At this high concentration (but lower total charge on pulp), the chemicals move as narrow, straight bands through the pulp mat. The high concentration will further enhance the bleaching rate, and increase the bleaching efficiency.

For this scenario, the industry would need to develop several gap filling technologies. These include:

* The development of a novel screen to meet the demanding process needs while resisting chemical attack

* A way to teed bleach chemicals uniformly to the undisturbed top surface of the pulp mat

* A way to collect any remaining unconsumed bleach chemicals and the different bleach filtrates. The latter can be done, for example, by adjusting the size and location of the collection areas under the novel screen, controlled by the on-line measurements of several pH or ion selective electrodes distributed along the length of the screen in the discharged effluent.

FURTHER DISCUSSION

There is potential for significant improvement in the way our industry processes forest resources. Selective processes can dramatically improve the value of the resources, and improved operational methods can significantly reduce the complexity and capital costs required. However, in addition to the process and technological gaps themselves, many enabling activities must first take place.

The industry needs commercial test facilities to prove designs and perform practical development work for such areas as high solids black liquor, modified recovery boilers, and modified recausticizing and fiber line processes. Yet no supplier can afford such a facility today, and no customer (pulp producer) will take the risk of experimenting with a mill-site prototype. The industry must develop partnerships and consortiums to balance the risk, manage the information gained, and spur developments and commercialization of these developments.

Acknowledgments: The author would like to acknowledge the contributions of the members of the breakthrough team for their assistance and contributions to this article, with special thanks to the Session Team Membership. In particular, the ongoing contributions of Olavi Tervo of Andritz-Ahlstrom, Adrian Van Heinengen of the University of Maine, and Gary Clark of the SUNY College of Environmental Science and Forestry at Syracuse are most appreciated.

ADDITIONAL RESOURCES:

* For Technology Summit information: www.tappi.org./ctosummit.asp

* The US. Department of Energy's Office of Industrial technology's home page: http://www.oit.doe.gov/forest/forest.shtml

Session Membership:

Rajai Atalla, Forest Products Laboratory

Dick Erickson, Weyerhaeuser

John Huyck, Mead Corp. (now MeadWestvaco)

Art Nonni, Georgia Pacific

Sandy Sharp, Westvaco Corp. (now MeadWestvaco)

Olavi Tervo, Ahlstrom (now Andritz-Ahlstrom)

Adrian Van Heinengen, University of Maine

About the author. John Huyck has 32 years experience in operations, engineering, and technology in the pulp and paper industry. He is currently ah executive with MeadWestvaco Corp. on assignment to the American Forest & Paper Association. Prior to his current assignment, he was director of corporate engineering for Mead Corp., Dayton, Ohio, USA. He joined Mead in 1984 and served in several management positions. Prior to Mead, Huyck worked for Wausau Paper Mills, Boise Southern, and Great Northern Nekoosa, He is a member of TAPPI, past-president of the Engineering Executive's Roundtable, AF&PA, and co-chair of the Capital Effectiveness Committee, Professional Interest in Technical and Organization Innovation. Huyck holds a BS in Paper Science from State University of New York, College of Forestry at Syracuse.