Reducing the environmental load of bagasse pulping and bleaching process

By maintaining the H-factor constant, the addition of a small fraction of AQ during cooking of bagasse reduced the Kappa number of pulp by almost 40% of that of soda pulp. Under specified process conditions, the oxygen pre-bleaching of soda and soda-AQ pulps also reduced the Kappa number by 45 and 49% of the original values for both pulps. However, the loss in yield and strength properties during oxygen pre-bleaching was very marginal for both soda and soda-AQ pulps. Thus, the reduced Kappa number of pulps decreased not only the demand of chemicals during bleaching, but also the formation of chlorinated organics. ECF bleaching of oxygen-delignified pulps gave higher brightness as compared to the DED bleaching of soda and soda-AQ pulps. The effluent properties, COD, color and AOX were significantly reduced by the increased substitution of chlorine with chlorine dioxide in the first and later stages of bleaching. A combination of oxygen pre-bleaching and DED bleaching would reduce the environmental load by 90% of that of CEH bleaching. So a pulp of higher brightness and comparable strength properties could be produced from bagasse by employing an environmentally friendly process of soda-AQ pulping, followed by oxygen pre-bleaching and DED bleaching.