ECF and TCF bleaching methods as applied to abaca pulp.

The performance of various ECF and TCF methods for bleaching cellulose pulp was examined. The former included the DED (chlorine dioxide-alkaline extraction-chlorine dioxide) method and the latter the hydrogen peroxide, peracetic acid, sodium perborate and OZP (oxygen-ozone-hydrogen peroxide) methods. The previous bleaching methods were applied to abaca pulp and their performance was compared in terms of the yield of bleached pulp, as well as the brightness breaking length, burst index and tear index of paper sheets made from it. Overall, the best results were those for pulp bleached with 4.5% peracetic acid at 55 degrees C for 30 min; the yield loss was very small (< 1 %) and the breaking length (6555 m), burst index (4.97 kN/g) and tear index (15.77 mNm(2)/g) were only 7.0%, 8.8% and 20.9% smaller than those for the starting, raw pulp. On the other hand, the brightness (77.4%) was 56.7% higher. Additional advantages of this bleaching treatment include the use of a lower temperature and shorter time, and so, therefore, less energy for heating, and also the need for smaller immobilized capital investments in industrial facilities. The DED and OZP treatments provide brighter pulp, albeit at the expense of increased yield losses, poorer paper properties, greater use of energy and chemical reagents, and more substantial investments in industrial facilities.