ABSTRACT
In this study, Total Chlorine Free (TCF) bleaching processes were evaluated for bleaching a secondary fiber of different origens. The samples were bleached to a target brightness of 78 % ISO. The results were interpreted on the basis of chemical cost to reach the target brightness, bleaching yield and bleached pulp quality as measured by viscosity, fluorescence and b* color coordinate. The ozone stage was responsible for improve TCF bleaching performance. The pulp bleached by sequences contained an ozone stage followed by chelation, without interstage washing (ZQ), and a final hydrogen peroxide stage unpressurized (P) or pressurized with oxygen (PO), designed as (ZQ)(PO) showed good results. These sequences decreased pulp b* coordinate significantly and fluorescence slightly. For all three bleaching processes, it was determined that process yield is negatively affected by hot alkaline stages such as oxygen, O, peroxide, P, and peroxide pressurized with oxygen, (PO) and also for the origin of the pulps of secondary fibers.
Key words:
secondary fibers; bleaching process (TCF)