A Decade Of Aq Benefits At Canfor's Northwood Mill (1994-2004), 2004 Engineering, Pulping, and PCE&I Conference

After 10 years of almost continuous usage at Canfor’s Northwood Mill in Prince George (B.C., Canada), anthraquinone (AQ) has proved its effectiveness as a digester additive for cellulose protection and increased delignification rate. Addition of 0.05% AQ on wood under standard Kraft pulping conditions at a normal target kappa number (i.e., 30.0) resulted in the following main benefits: a minimum increase in absolute digester yield of 0.8% (1.2% average), chip usage reduction of 1.8% minimum (2.6% average), a reduction of 3.5% in alkali charge, and a 5% reduction in black liquor solids produced/ton of pulp. Changes in pulp strength parameters included a 10% reduction in refining energy, 2 to 3 cp increase in bleached pulp viscosity, slight increase in tensile, and slight decrease in tear. Other minor benefits included reduced cooking temperatures.

A discussion will review the mill’s two continuous Kamyr digester fiberlines (A line= conventional + oxygen delignification and B line= MCC (during initial years) and Lo-Solids cooking later).

Four different methods were used to validate the performance of AQ: black liquor solids produced/ton of pulp, chip usage factor (CUF), chip meter fill factors, and carbohydrate analyses. The obtained data will be discussed and its validation will be corroborated.

Economical benefits will be presented. These benefits are mill dependent based on the cost of wood, pulp, AQ, and energy as well as the bottleneck areas of each mill.