Improving the Efficiency of a Two-Stage Oxygen Delignification System, 2004 Engineering, Pulping, and PCE&I Conference
The Botnia Joutseno bleached kraft pulp mill has a two-stage oxygen delignification system prior to a three-stage
ECF bleach plant. The temperature in both oxygen stages was 90°C or higher. Most chemicals were charged in the
first stage, but smaller doses were charged in the second stage. The most modern oxygen delignification
applications from machinery suppliers, however, suggested that lower temperature would be beneficial in terms of
pulp quality and yield. With the help of a new heat exchanger, the temperature in the first oxygen delignification
stage was reduced to about 83°C. Moreover, all the chemicals were charged in the first stage. The pulp and filtrate
samples from the oxygen delignification system were collected during two one-week mill trials and then
characterized. According to the results from the pulp and filtrate analyses, these process changes improved postoxygen
pulp quality and yield.
Improving the Efficiency of a Two-Stage Oxygen Delignification System, 2004 Engineering, Pulping, an