Superior Tools for Adjustable Screening Process Metso Paper - - PowerPoint PPT Presentation

Superior Tools for Adjustable Screening Process Metso Paper Valkeakoski Oy, Finland Minna Puro 8th Research Forum on Recycling

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Content of the presentation

• Introduction
• Numerical study
• Results
• simulation results
• pilot trial results
• Conclusions

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Introduction

• Operational demands set for DIP screening

have intensified

• raw material contains more and more impurities
• accept pulp quality has to remain at high level
• economical and environmental aspects become more significant
• Intensifying demands force us to use

narrower slots

⇒ capacity problems ⇒ strong reject thickening ⇒ remarkable operation problems and fiber losses with conventional

technology

⇒ new foil and screen basket technology was needed

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Numerical study

The basic data of simulated foils and baskets

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accept frame rotor frame basket periodic boundaries

static pressure [Pa]

• 2D periodically

symmetric slice

• screen basket

modelled as a porous media

• no inlet or outlet
• different viscosity

values tested

Foil simulations

• Flow geometry

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• 2D periodically

symmetric section

• constant slot width

#0.12 mm

• constant 0.5 m/s

tangential velocity on the accept side

• water material

properties

Screen basket simulations

• Comparison of different wire designs
• slot speeds 1–10 m/s

corresponds foil-induced

• tangential velocity 0,5 m/s

pulsation on the feed side

feed accept wires periodic boundaries

static pressure [Pa]

}

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Simulation results of foil study

• New foil shape - ProFoil
• very effective suction pulse
• less co-rotation

ProFoil

radial velocity tangential velocity

Conventional foil ProFoil

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Simulated foil pressure pulses results

• New foil shape
• adjustability in respect to foil speed

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Simulation results of screen basket wire study

• New wire shape - Nimax
• smooth and streamlined accept channel
• optimised basket surface shape

Nimax wire Conventional wire

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Simulation and measured pressures

Screen basket wire study

• Good correlation between simulation and measurements

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Foil pilot-scale trial results

Capacity study

• Comparison of reference and new foil
• with #0.12 mm narrow slot and reference foil, plugging occurred

at 0.8 m/s slot speed ⇒ too low capacity

• with #0.12 mm narrow slot and new foil, operation was excellent

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Foil pilot-scale trial results

Energy consumption study

• Comparison of reference and new foil
• with #0.12 mm narrow slot, new foil used 10 % less energy than

reference foil

• energy saving can be even 30 % less as reported in one

customer project

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Foil pilot-scale trial results

Reject thickening

• Comparison of reference and new foil
• reference foil is not in operation window with narrow #0.12 mm

slot due to very strong thickening

• new foil fulfilled the target of controlled thickening regardless of

slot size and reject rate

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Foil pilot-scale trial results

Stickies

• Comparison of reference and new foil
• quality is at the same level with new foil and reference foil when

running with #0.15 mm basket

• with narrow #0.12 mm slot high quality was reached with

reasonable low reject rates

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Screen basket pilot-scale trial results

Capacity study

• Comparison of conventional wires (A, B) and new wire
• new wire gives 20 % more capacity

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Screen basket pilot-scale trial results

Energy consumption study

• Comparison of conventional wires (A, B) and new wire
• new wire energy consumption is 10 % less than conventional

wires

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Screen basket pilot-scale trial results

Reject thickening

• Comparison of conventional wires (A, B) and new wire
• new wire gives low level of thickening

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Screen basket pilot-scale trial results

Stickies

• Comparison of conventional wires (A, B) and new wire
• quality is at the same level with new foil and conventional foils

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Conclusions

Major benefits

• By combining the new screen basket wire

with the new foil design, optimal screening result can be summed up:

• 20 - 30 % more capacity
• 10 - 30 % energy saving
• 10 - 20 % less thickening
• excellent pulp quality
• excellent runnability