ATMOS Premium Tissue I Energy efficiency – A challenge for ... - Voith

TECHNOLOGY
48
Ruzomberok, a town with 35,000 inhabitants
in the hilly Zilinas region
of Slovakia, has been involved in
papermaking since the seventeenth
century. Mondi Paper is one of the
region’s biggest employers and operates
Slovakia’s largest pulp and
paper mill. In 2004, when various
dryer fabrics of different makes and
designs were in use, Mondi assigned
Voith Paper Fabrics with efficiency
analysis of the rebuilt dryer section.
The goals were as follows: improve
drying efficiency, solve the web run
problems, and optimize fabrics
performance throughout the dryer
section.
Improved drying
The following analyses were carried
out in two days: drying efficiency,
heat transfer (steam, cylinder surface
and web temperatures), pocket con-
ditions, hood air conditions, hood
supply and exhaust air, pocket airflow
conditions, and web shrinkage. After
shutdown, the machine and fabrics
were then examined in detail to
determine improvement potential.
The study of the dryer section showed
a high specific steam consumption
of 1.33 to 1.39 kg of steam/kg of
evaporated moisture. Pocket moisture
content amounted to 700 g/kg,
thus reducing the evaporation rate.
Spiral fabrics with low air permeability
normally have elliptical spirals.
As a result the web is only supported
on a few small contact points, which
can cause marking and non-uniform
drying. Voith Paper Fabrics, therefore,
developed the levelling process for
the PrintTech LBR spiral fabric with
low air permeability. This increases
the contact surface area on the web
side, resulting in more uniform drying
The levelling process shown on the right
increases the contact surface area and
resistance to abrasion
and less risk in marking high quality
paper grades.
Following the successful use of Print-
Tech LBR spiral fabrics in the second
and fourth single-tier dryer group
(TopDuoRun) in May 2005, Voith
Paper Fabrics spiral fabrics were installed
throughout the PM 18 dryer
section. The measurements carried
out in 2006 showed improved drying
rates, and reduced specific steam
consumptions of 1.18 to 1.19 kg/kg.
A higher evaporation rate with lower
steam consumption brings energy
cost savings, adding value from the
dryer fabrics.
Improved web run
The dryer section showed high readings
for inflowing air (negative values)
on the wet side and high readings for
outflowing air (positive values) on the
dry side at the web edge. This airflow
PrintTech LBR spiral fabric Energy savings achieved by replacing all dryer fabrics with PrintTech LBR
Date
29.04.04
21.04.05
22.03.06
PrintTech LBR on 70% of positions
24.10.06
PrintTech LBR on 100% of positions
Steam used
(kg steam/kg evaporated moisture)
1.33
1.39
1.19
1.18
Evaporation rate
(kg/hr/m 2 )
24.25
23.06
26.92
27.15
24 I 2007 I Voith Paper I twogether