Chelating agents management to obtain TCF bleached eucalyptus grandis kraft pulps. I: Selecting the best sequence

AREA, M.C.; FELISSIA, F.E.

Sao Paulo, Brasil

Congreso; 36º Congresso e Exposição Internacional de Celulose e Papel. ABTCP-TAPPI 2003; 2003

ABTCP

This work studies phosphonates performance when added in laboratory Kraft Eucalyptus grandis TCF bleaching (O-Q-Op-P). Design (16 final pulps) included sequences of brown stock washed with DTPMPA, a control using a classical EDTA Q stage, EDTA and DTPMPA combinations, and Q stage elimination. Results show that Mn and Fe content in pulps are not statistically different when applying a Q stage with the same quantity of EDTA or DTPMPA. Metals removal is more efficient when chelant load is distributed between stages, than when applied only in a Q stage. Chelant incorporation in O stage washing water improves noticeably pulps brightness. The best choice includes DTPMPA in brown stock washing, elimination of the Q stage, DTPMPA in Op stage, and DTPMPA in P stage. Optimizing the P stage of this sequence can result in 50% of peroxide residual, which can be recycled to the Op stage.