Paper Technology International 2020 - Journal - Page 55

PAPERTECHNOLOGYINTERNATIONAL
Dewatering to improve: Oradoc tips to drain the right way.
Andrea Giuntini, MTK Application Engineer, Oradoc
INTRODUCTION:
Vacuum and dewatering systems are crucial for papermaking, as they contribute to sheet formation, press performance, felt
conditioning and general machine efficiency.
In spite of that, paper machines usually operate paying little attention to vacuum processes, until these systems tend to evolve into
lost performance, often resulting in reduced dewatering capability, slow or variable drainage, which has a direct and negative impact on
overall paper machine efficiency and operating costs.
Other problems may include as well vacuum pump reliability and maintenance problems, thus contributing to downtime.
With regard to dewatering systems, Oradoc stands out for its
long-standing experience gained in tissue paper plants and, thanks
to the recent acquisition of MTK, can now also boast an in-depth
knowledge of vacuum and drainage systems specifically conceived
for paper and cardboard production lines.
One of the most recent and meaningful intervention was
carried out at Papeles y Corrugados Andina S.A., in Colombia, a
company dedicated to the manufacture and marketing of corrugated
cardboard packaging solutions, which entered its national paper
market in 1995.
Understanding how the early vacuum table should be set
up is fundamental: good formation requires gradual dewatering
to properly develop the sheet and failure to control early vacuum
elements can generate, instead, aggressive dewatering.
Given that the vacuum system includes several sub-systems
for vacuum control, air/water separation, and vacuum pump seal
water management, it is extremely important to correctly size all
various components that are part of the vacuum system: in this
case, an expert advice can really make a difference in choosing the
best configuration to get the most out of dewatering.
Figure 1: Overall vacuum system layout with drainage elements
and wire before start-up.
Figure 2: Vacuum system layout.
Currently, Papeles y Corrugados Andina S.A. production
plant produces kraftliner packaging paper with weights ranging from
125 to 300 gr/sqm, a paper width of 2450mm and a max production
speed of 400 m/min, reaching approximately 3,600 tons/month
of paper, while the corrugator production plant has a capacity of
7,000,000 sqm/month.
As it sometimes happens in most paper production plant,
the Andina one in Colombia was suffering slow initial drainage and
poor formation; that’s why we proposed an overall rebuilding of
the wet area and a brand new vacuum system to boost drainage
performances.
As early vacuum table operation, formation and sheet quality
are closely linked, lack of understanding of how these systems are
meant to work may have significant consequences on final product’s
quality.
When it comes to vacuum, ‘virtue stands in the middle’,
as the saying goes, which means that lack of accurate vacuum
measurement and control - too low or excessive vacuum - may
damage papermaking in the same way. Good formation needs
gradual dewatering to develop the sheet, while failure to control
early vacuum elements can entail aggressive dewatering.
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