Authors: Olavi Pikka1, Sami Siik1, Marco Andrade2, Ronny Geiger2, Viridiane Vianna2, Leonardo Pimenta3, Tiago Segura3,
Francisco Mattiazzo3, Davi Apparecido3
1 Andritz OY. Finland
2 Andritz Brasil Ltda. Brazil
3 Eldorado Brasil Celulose. Brazil
ABSTRACT
Modern eucalyptus fiberlines are frequently challenged to
produce high quality pulp with a small content of shives and
sand. Not only production increases, but also optimization to
reduce input costs, require efforts to maintain pulp quality. It
is predicted that Brazil’s increase in bleached hardwood kraft
pulp (BHKP) production will reach 3.5 Mtons/year in 2022.
The screenroom area was investigated as it is responsible for
removing shives and sand from the pulp. Different periods
were investigated in a modern fiberline screenroom plant in
order to identify and compare total shives and sand (total
ash) profiles. The screenroom system consists of knots
separation, primary, secondary and tertiary screening, knots
and rejects washers, shive cleaners, sand cleaners and sand
separation screw. Knots are sent back to cooking and shives
are partially returned to oxygen delignification. The aim of
this study was to compare total shives and sand (total ash)
profile from different periods. Results of shives profile,
shives and fiber losses, shives and sand balances are shown
in this study. Shives profile indicated that although the shives
content from the digester varied for the different periods,
the shives content in screening feed and accept remained
constant. A variation is seen in shives discarded from the
process for the different periods. More recently, this discard
has increased more significantly from the knot washer.
Satisfactory efficiency was observed in total shives removal
in screening: 89-90% for combi-screens, 95% for secondary
screen, 93-95% for tertiary screen and 72-84% for the shive
cleaners. For sand (total ash) removal, the overall efficiency
did not change significantly and the removal efficiency in
fiberline increased from 61.0% to 66.5%.
Keywords: shives, screenroom, fiberline, profile study.
O PAPEL vol. 80, num. 06, pp. 83 - 89 - JUN 2019