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8 TAPPSA JOURNAL | VOLUME 2 2013
SCREENING & CLEANING
Trends in ScreeningScreening requirements have
changed over the years, due to the inferiority of raw material for paper and pulp production as well as the
increasing cost pressures requiring energy-effi cient products or
process optimisations. In addition, all manufacturers have had to increase system effectiveness
in order to compete and be sustainable in the globalised pulp
and paper industry environment.
Voith, being a global system supplier, has been in a position to make the most of these developments to revolutionise energy use in the industry. The company now provides optimised screening components and systems know-how for all kinds of single screen and complex system applications.
The company’s revised product portfolio offers highly engineered Performance Enhancement Components (PEC) using modern, innovative manufacturing techniques to meet functional requirements. Whatever the application, Voith offers high-quality rotor and cylinder products for pressurised screens. This includes Voith machines or as individually designed rebuild PECs to replace the original installed equipment in non-Voith machines.
Process improvements through ScreenFit™ TechnologyFrom the beginning to the end, there’s Voith ScreenFit™ technology. Voith is able to equip all stages of the manufacturing process covering coarse and fi ne screening within stock preparation and broke as well as approach fl ow screening.
Drawing on the company’s background knowledge of long-term process optimisation, Voith’s ScreenFit™ concept has helped customers to realise their individual objectives for their screening systems. The ScreenFit™ Navigator platform is a benchmarking tool that analyses the actual energy effi ciency performance of different screen systems from their operational process data. This is followed by a free and non-binding consultation to analyse in greater depth the possibilities for further improvements and steps to be taken if the screening system is not up to standard.
ScreenFit™ InnovationsProducts, Sets and Applications
8 TAPPSA JOURNAL | VOLUME 2 2013
TAPPSA JOURNAL | VOLUME 2 2013 9
EclipseRotor™ - SeriesThe EclipseRotor™ was developed to screen thick stock and heavily contaminated stock applications using a new hydrodynamic foil shape. This foil uses smooth pressure and a strong suction zone to achieve up to 25% higher capacity and subsequently lower energy consumption.
The EclipseRotor™ - Series is ideal for service in the stock preparation for all kinds of grades as well as for Virgin Pulp screening.
The EclipseRotor™ - Series is ideal for
The re-engineered MultiFoil™ Rotor reduces energy demand by up to 15%, resulting in maximum effi ciency and excellent wear resistance through its unique and patented foil design.
The MultiFoil™ Rotor E-Series is applied in stock preparation for all kinds of grades.
MultiFoil™ Rotor - Economy SeriesExcellence in Voith engineered
productsScreening technology and effects are infl uenced through several operational parameters, including the composition and quality of the raw materials or the selection of screen baskets and rotors. For the latter, Voith provides next-generation screening technology for all kind of grades like Graphic, Board & Packaging and Specialty paper as well as Virgin Pulp screening applications.
The especially reinforced slotted C-bar™ basket was developed to cover high-shear and thick-stock applications using up to doubled screening area. Its unique stability results in a long life and reliable screen operation.
The C-bar™ M is suitable for replacing conventional milled slotted or wedge wire cylinders as well as cartridge models from other suppliers in stock preparation and Virgin Pulp screening applications.
C-bar™ - M Slotted Basket SeriesSlotted Basket
Excellence in Voith engineered products
Case study: ASIA
SCREENING & CLEANING
The ScreenFit™ Doctors’ fi rst assignment was at a board and packaging plant in southern China. The initial analysis revealed that the plant’s Metso-Tampella fractionator was operating with accepted stock that had an extremely high sticky concentration of 7,300 mm²/kg and that the rotor was running at its maximum output. In addition, the continual formation of spinnings in the slot basket signifi cantly reduced overall screening effi ciency. Here, the customer’s requirements were to improve the machine’s screening effi ciency and reduce its energy consumption.
10,000
8,000
6,000
200
150
100
50
0
4,000
2,000
0,000
154
106
7300
3891
Decrease in power consumption
Decrease in sticky concentration in accept
BEFORE REBUILD AFTER REBUILD
Powe
r con
sum
ptio
n [kW
]
Stick
y con
cent
ratio
n acc
ept [
mm
2 /kg]
Asia results case study with MultiFoil™ Rotor
Continued on following page.
10 TAPPSA JOURNAL | VOLUME 2 2013
Asia case study, continued:
To achieve these goals, Voith Paper’s Doctors upgraded the plant’s fractionator with proven C-bar™ Screening Technology and a new MultiFoil™ rotor. In China, operational testing by the customer resulted in signifi cant improvements:
A streamlined MultiFoil™ blade profi le eliminated the spinning problem.
Energy consumption was cut by 30%.
Sticky concentrations in the accepted stock were reduced by 50%.
As a result of these improvements, the customer could save approximately R320 000 per year and reduce CO² emissions by 18.7 tonnes per year.
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A rotor of a non-Voith TLA 450 screen with spinnings at the foil blades.
A rotor of a non-Voith TLA 450 screen with spinnings at the foil blades.
SCREENING & CLEANING
At a LWC paper mill in Germany, the ScreenFit™ Doctors had to reduce the mill’s energy consumption by 20% and improve the paper mill’s overall output − without compromising the quality of the raw stock processing.
When the Voith Paper Doctors arrived, the customer’s DIP tailing screen MST 05/05 was equipped with a step rotor and a Contour basket, which was operating with a 4% pulp consistency and a tip speed of 20 m/s. Here, the ScreenFit™ Doctors installed the newly developed, energy-saving Rotor Eclipse™ F, with a streamlined blade profi le. The results were convincing:
Case study: GERMANY
100
80
60
30
20
10
0
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20
0
20
1540
60
Decrease in power consumption
Increase in screeningeffi ciency
BEFORE REBUILD AFTER REBUILD
Powe
r con
sum
ptio
n [kW
]
Scre
enin
g effi
cienc
y [%
]
Europe results case study with Rotor Eclipse™ F and contour basket
Hole Screen Basket Contour-
type
Extensive tests on the customer’s machine showed energy consumption cut by 25% while output simultaneously increased 20%.
Additionally, the new rotor improved screening effi ciency by 20%.
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TAPPSA JOURNAL | VOLUME 2 2013 11
SCREENING & CLEANING
ScreenFit™ Compass 2011In the benchmark ScreenFit™ Compass 2011 study, Voith Paper analysed 80 fi ne-screening systems of various generations, makes, models and sizes. The results were clear: 70 % of screening processes analysed worldwide use energy ineffi ciently.
The ScreenFit™ Compass process identifi ed only 24 of the 80 systems as energy-effi cient. Twelve were in the mid-range for energy effi ciency and have clear possibilities for improvement. The remaining 44 systems proved ineffi cient, with a very high optimisation potential.
In the study, the designs of 80 stock-preparation systems worldwide were compared to the current state-of-the-art technology. The fi ndings rated the energy consumption of various manufacturers, based on stock consistency, screening effi ciency, operating mode, and paper grade. A full-cascade system consumes more specifi c energy than a partial-cascade system because the full cascade returns stock to the upstream stage. Operating in full or partial cascade, however, depends upon technical factors such as screening effi ciency and cannot be made dependent on the specifi c energy requirement. The specifi c power input refers only to the screening machines in the study. Pumping energies were not taken into account in the calculation.
The wrong choice of screening concept or operation of obsolete systems appear to be the main causes of the poor results in the ScreenFit™ Compass 2011. To counter those poor results, Voith Paper offers its C-bar™ screen basket line, which continues to be enhanced with ongoing innovations. Over the past few years, the relationship between screen basket size and screen surface has constantly increased with C-bar™ family baskets while slot widths have stayed constant. As the latest screen baskets get smaller in size, production capacity increases, and screens once operated in parallel can be switched off. Investment and operating costs can thus be substantially reduced.
Along with the right choice of screen baskets and rotors that match them (e.g., the MultiFoil™ rotor), stock consistency and the interconnection of the individual screening stages contribute considerably to specifi c energy consumption. For this reason, modern Voith stock-preparation concepts aim at increasing stock consistency and improving the relation between energy input and screening effi ciency. The compact design of the new screening systems reduces the size of the stock preparation, which in turn leads to lower investment costs. However, choosing the right screen basket depends not only on open screen surface but also on stock parameters, such as fi bre length.
Free benchmark test on the InternetVoith Paper has now created a way to subject the fi ne screening for brown and graphic paper to a quick, non-binding selftest via the Internet (www.ScreenFitNavigator.com). The calculation for this initial check is based on the results of the screening system study. System operators need only name the system type, identify a few parameters, and give information on the main screening quality focus for the screening. The programme then draws up an initial energy evaluation of the screening system. The energy effi ciency of the system becomes visible on a colour bar from green to red. ■
For more information on these and other products, please email [email protected]
