Paper Technology International 2024 - Journal - Page 95
PAPERTECHNOLOGYINTERNATIONAL
rebuilding:
DDryer section doctors’
bene昀椀ts breakdown
Sara Giunchi, Communication Manager Oradoc Srl
INTRODUCTION:
Dry your pulp up, not your budget: how a doctors’ rebuilding in the dryer section may help improve overall performances without
draining 昀椀nances.
Figure 1: Dryer section (above) Figure 2: OraClean (right).
The dryer section: [1] of a paper machine removes between
1.1 and 1.3 kg of water per kg of paper; removing water at this
production stage is signi昀椀cantly more expensive than in any other
section of the machine: this easily explains why the dryer section
is by far the largest consumer of thermal energy within the paper
machine.
Often considered as something like a black box for the
complexity of the paper drying process, the drying section is where
the magic actually happens: thanks to heat transfer, evaporation,
water removal, hoods and hot cylinders, the slurry pulp turns into
paper with approx 90/95% of solid content.
That’s why the operation of a dryer section must be
optimized in terms of both heat transfer and water removal.
The silver lining is that energy ef昀椀ciency can be improved
with quite modest investments: enhancing doctoring may help mills
boost cylinder drying capacity and runnability, while achieving better
paper quality and higher production ef昀椀ciency, reducing power
consumption as well as operating costs.
When asked to improve the performance of the paper
machine in the drying area, Oradoc carefully considers the critical
positions in a drying section, i.e. the beginning and the end of the
drying section, where doctors in some cases are also employed
to detach the paper from
the last drying cylinder and
directing it either to the
pulper tank or to the pope
or size press. When poor
performances go along with
critical wear conditions, a
complete doctors’ rebuilding
is often the wiser choice
to ensure optimal cleaning
performance even at higher
machine speed.
Confronted with
a customer request, who
was trying to solve some issues in the dryer section, Oradoc
proposed its well-known OraClean [2]: the rigid doctoring system
to ensure correct and uniform cleaning of the dryer cylinder, with
a simple construction that guarantees easy maintenance and
easy replacement of the blade. The supply also included doctor
back, supports, bearings and electro-mechanical or pneumatic
oscillation system, which can be con昀椀gured according to customer
speci昀椀cations, offering options of manual execution or via pneumatic
cylinders.
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