ABSTRACT
In this study, cooking of the wood had been investigated until kappa numbers 17 and 14 for a process kinetically modified, elimination of oxygen delignification from the fiber line, and application of AD(EO)D and AD(PO)D techniques for pulp of kappa 17 and AD(EO)D and DHT(EPO)DP for pulp of kappa 14 for the bleaching at 90% ISO. As references, cookings had been carried out until kappa number 17 and 14, oxygen delignification in simple stage and conventional bleaching with sequences A/D(EO)D, A/D(EPO)D, A/D(EO)DP and A/D(EPO)DP for the kappa number 17 pulp and oxygen delignification in simple stage and conventional bleaching sequence DHT(EPO)DP for pulp of kappa 14. For the pulp of kappa 17, one concluded that processes AD(EO)D and AD(PO)D produced pulp of brightness 90% ISO with good viscosity and brightness stability, using TAC´s (totally active chloro) relatively low, and it’s not necessary the oxygen delignification. Amongst these two processes, the first one revealed to be more attractive to reach the level of 90% ISO brightness. However, comparatively to the reference processes, with oxygen delignification, for example O-A/D(EPO)DP, process AD(EO)D results in increase of the operational cost of the order of US$7-8/odt, including wood and reagents. For the kappa number 14 pulp, process AD(EO)D also revealed to be attractive, but the sequence DHT(EPO)DP was the one that used lower TAC`s; however, when compared with the reference (O-DHT(EPO)DP), it resulted in an increase of operational cost of the order of US$5/odt. Therefore, it can be concluded that the alternative process, without the deslignification with oxygen, is viable only for pulps of lower kappa number.
Keywords:
modified cooking; bleaching; delignification degree and Hexenuronic acid