Impact of Various Enzymes on Conventional Bleaching Process, 1996 Pulping Conference Proceedings

Bindu Dhasmana and Kevin Taylor

Jeffery S. Hsieh

Georgia Institute of Technology

Today general concern about the environmental impact of chlorine bleaching effluents has led to a trend towards elemental chlorine free or total chlorine free bleaching methods. One of the most recent technology, adapted to reduce the chloro-organic compounds in bleach plant effluents is application of enzyme before or during bleaching process. Effectiveness of various enzymes (Enzyme A, B and C) on pulp delignification and their impact on bleachability of pulp were studied in detail. Conventional bleaching sequence (CEDED) was used to achieve full brightness (+80% ISO) pulp. Three different kappa factors were used to determined the effect of different chlorine charges. Higher delignification (1-3 units more kappa drop) was observed in all the enzyme treated pulp than control pulp after chlorination. Higher brightness and lower kappa number at subsequent stages of bleaching was noticed for all the enzyme treated pulp compared to control pulp with no enzyme treatment. Samples pretreated with enzyme yielded a pulp of final brightness 82.5- 89.4% (ISO) compared to final brightness 79.0-87.3% (ISO) of control pulp. Higher brightness was achieved for all the enzyme treated pulp with much lower bleaching chemicals compared to control sample. To reach same level of brightness 15% -22% chlorine can be saved using enzyme before chlorine stage. The use of enzyme in alkali extraction stage did not show any promising results.