Canfor / AFT Partnership

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The situation

"Installing the new AFT Gladiator HC™ rotor has substantially reduced our electricity consumption while increasing our screen throughput and maintaining overall pulp quality."

— Ed Dylke, Manager of Technical Development, Canadian Forest Products

Pulp and paper manufacturing is an energy-intensive industry. Therefore, any improvement in energy efficiency at one of B.C.'s 20 pulp and paper mills cannot only offer significant energy savings to individual facilities, but can also reduce the province's overall industrial energy consumption.

One high-energy process in pulp and paper mills is the use of pulp screens to remove contaminants from the pulp. A rotor inside the cylindrical screen spins the pulp at high velocity, forcing it through narrow apertures in the screen, which serves as a barrier to debris, contaminants and uncooked or undeveloped wood fibre bundles (shives). This makes shive-free pulp available for further processing. The screens are critical in ensuring the quality of the pulp, which in turn affects the quality of the resulting paper products.

There are an estimated 300 pulp screens in the province. For some time, mill managers and energy experts have been looking at the potential for energy savings by reducing rotor speed. However, this must be done in a way that does not compromise the screens' performance in removing contaminants. Searching for a more energy-efficient screening method was the focus of a recent demonstration project at Canfor's Northwood Kraft Pulp Mill in Prince George.

The solution

Advanced Fiber Technologies (AFT) of Montreal, Quebec, is the world's leading producer of customized screening solutions for the pulp and paper industry, and has been in operation for more than 100 years. In collaboration with researchers at the University of British Columbia (UBC), AFT developed a new high-capacity, low-energy pulp screen rotor technology called the Gladiator HC™ rotor. To demonstrate the performance of the new technology in the field, Canfor, AFT, UBC, BC Hydro, and Natural Resources Canada partnered to test and demonstrate the new screen operation at the Canfor mill. Starting in the fall of 2005, this very successful project was completed in early 2006.

Two new AFT rotor designs: The EP™ rotor (left) and the Gladiator HC™ rotor (right)

During the trial, the speed of the Gladiator HC™ rotor was varied from 29 metres/second (the speed of the existing rotor) to the lowest possible speed before the screen started to plug, while keeping the screen feed flow rate constant.

The benefits

Energy savings and productivity
The trial found that the Gladiator HC™ rotor showed results well beyond expectations, reducing electricity consumption by 52% – achieving 60.8 kilowatts of electricity savings – while producing the same or higher tonnage with similar shive removal efficiency. Over the course of a year, the mill could save 3.58 gigawatt hours (GWh), or $193,000, if all its screen rotors were replaced. If all 300 pulp screens used in B.C. mills were converted to these rotors, estimates are that 153 GWh of electricity could be saved province-wide each year. This represents over $8-million of electricity cost savings.

Competitive cost
The cost of the Gladiator HC™ rotor is similar to that of other rotors currently in use.

Maintenance and life cycle cost savings
Maintenance costs on the screen assembly should be reduced because the Gladiator HC™ rotor allows the screen to run at a slower speed. This should reduce rotor and screen wear due to abrasion, and extend the life of the rotor and cylinder, as well as the bearings, seals, and drive belts. In some applications in other countries, the Gladiator HC™ rotor has lengthened the life of the rotor and cylinder by 20%. Also, the larger gap between the rotor and cylinder should help prevent failure of the cylinder when large rocks or metals enter the screen.

A growing province. A growing challenge. In the next 20 years, B.C. will require between 25% and 40% more electricity than we use today. While it's not the whole answer, conservation is the first, best choice for starting to meet that need.