Computer software, chemical engineering and cutting edge technologies - all are used by pulp-and-paper mills

Invented in China two thousand year ago, paper has long been an all-pervasive feature of our lives. Homes, offices, schools - even our streets are littered with it. Many remember making paper in elementary school from vegetable scrap and newsprint. So is it any wonder that most people assume paper production to be a strictly low tech activity?

Contrary to popular perception, however, this high-output industry employs a wide range of advanced technologies from computer software to chemical engineering.

The Mechanical Wood-Pulps Network, a federally-funded Network of Centres of Excellence, is developing new technologies that will enable Canadian paper mills to manufacture high-quality products from mechanical pulp processes.

Mechanical-pulp paper, such as newsprint, is made by separating wood fibres by mechanical means to produce pulp. Mechanical processes produce a much higher yield of pulp than chemical processes. The reason for this is that chemical processes dissolve all the lignin, the substance that binds the wood fibres together. In contrast, mechanical processes simply degrade the lignin, so that the wood fibres fall apart. While this leads to a greater yield of pulp, the paper produced tends not to last as long, since lignin turns paper yellow when it ages.

According to Dr. George Rosenberg, the Managing Director of the Mechanical Wood-Pulps Network, an objective of the network is to produce higher quality paper from mechanical-pulp by improving the quality control or process control in paper production.

Process control involves fine-tuning each stage of the paper making process in order to improve the consistency and quality of the final product. Researchers at the Mechanical Wood-Pulps Network are developing software and equipment to enhance process control in paper mills.

Guy Dumont, an electrical-engineering professor at the University of British Columbia is the program leader for the Mechanical Wood-Pulps Network process control program. Software developed by Gumont such as, BrainWaveä and PPC Wavelet Toolbox are designed to keep each stage of paper production at peak performance targets. These computer programs have already been successfully implemented in paper mills in Alberta.

Chad Bennington, a chemical-engineer at the University of British Columbia, is designing quality control devices to ensure good mixing and more uniform flow from blend chests. Blend chests are used to combine wood fibres and other chemical additives for making paper. With the increasing speed of paper machines it is important to minimize variations in blend chests to maintain efficient mixing. A model blend chest has already been designed, constructed and implemented.

Michel Perrier, a chemical-engineering professor at the École Polytechnique in Montreal, has developed software to control the level of fines (wood particles) that are extracted from pulp water. Regulating the quantity of fines in pulp will help improve the quality of the paper produced.

Sirish Shah, a chemical-engineering professor at the University of Alberta has worked on developing process control loops to regulate variables in paper production. A common example of a process control loop are thermostats inside homes. Thermostats regulate warmth by measuring room temperature with a sensor and comparing the temperature to the thermostat setting. If the temperature dips below or rises above the setting, the thermostat sends a signal to the furnace to either raise or lower the level of heat. A process control loop in a paper mill keeps important variables such as voltage, pressure or flow rate from wandering beyond preset operating limits. Regulating the consistency of the variables ensures a more uniform final product.

These are just a few projects that 41 professors, 34 industry-researchers and 63 grad students funded by the Mechanical Wood-Pulps Network are currently working on to make Canada's pulp-and-paper industry world leaders in the manufacture of mechanical-pulps paper.

by Michael Rappaport